starting from commit 6daad64277c43a6589de1c6a146ca8a72fe0e3b9 attempts to use the org-capture template expansion "%x" results in the following backtrace:

Debugger entered--Lisp error: (error "Capture abort: (wrong-type-argument char-or-string-p nil)")
  signal(error ("Capture abort: (wrong-type-argument char-or-string-p nil)"))
  error("Capture abort: %s" (wrong-type-argument char-or-string-p nil))
  #[257 "\300\301!\203\n\302\301!\210\303\304\"\207" [get-buffer "*Capture*" kill-buffer error "Capture abort: %s"] 4 "\n\n(fn ERROR)"]((wrong-type-argument char-or-string-p nil))
  funcall(#[257 "\300\301!\203\n\302\301!\210\303\304\"\207" [get-buffer "*Capture*" kill-buffer error "Capture abort: %s"] 4 "\n\n(fn ERROR)"] (wrong-type-argument char-or-string-p nil))
  org-capture(nil)
  call-interactively(org-capture nil nil)
  command-execute(org-capture)

Older versions work just as described in http://orgmode.org/manual/Template-expansion.html

---


Emacs  : GNU Emacs 24.5.1 (x86_64-pc-linux-gnu)
 of 2016-07-25 on cervinia
Package: Org-mode version 8.3.4 (release_8.3.4-892-g480d35 @ /usr/share/emacs/site-lisp/org-mode/)

current state:
==============
(setq
 org-hide-leading-stars t
 org-hide-block-startup t
 org-tab-first-hook '(org-hide-block-toggle-maybe org-babel-hide-result-toggle-maybe
                      org-babel-header-arg-expand)
 org-habit-preceding-days 10
 org-speed-command-hook '(org-speed-command-default-hook org-babel-speed-command-hook)
 org-agenda-category-icon-alist '(("io"
                                   "/usr/share/icons/gnome/16x16/status/weather-fog.png"
                                   nil nil :ascent center)
                                  ("habit" "/usr/share/icons/gnome/16x16/mimetypes/deb.png"
                                   nil nil :ascent center)
                                  ("imparare"
                                   "/usr/share/icons/gnome/16x16/mimetypes/contents2.png"
                                   nil nil :ascent center)
                                  ("solere" "~/.emoj/small/Emoji_Natur-116.png" nil nil
                                   :ascent center)
                                  )
 org-clock-history-length 28
 org-ellipsis " ⌟"
 org-occur-hook '(org-first-headline-recenter)
 org-metaup-hook '(org-babel-load-in-session-maybe)
 org-clock-into-drawer "orologio"
 org-src-window-setup 'current-window
 org-confirm-shell-link-function 'yes-or-no-p
 org-columns-default-format "%20ITEM(item) %10TODO(fare) %10SCHEDULED(scheduled) %TAGS"
 org-speed-commands-user '(("N" . clockin-nope) ("W" . clockin-web) ("J" . org-clock-goto))
 org-clock-idle-time 20
 org-habit-completed-glyph 10003
 org-file-apps '((auto-mode . emacs) ("\\.mm\\'" . default) ("\\.x?html?\\'" . default)
                 ("\\.pdf\\'" . emacs))
 org-special-ctrl-a/e t
 org-agenda-custom-commands '(("f" occur-tree "FIXME"))
 org-return-follows-link t
 org-default-notes-file "ciaparme/incollati.org"
 org-clock-in-resume t
 org-habit-following-days 3
 org-capture-templates '(("f" "facendo" entry (file "roba/facendo.org")
                          "* TODO %^{soggetto}       %^g\n  - %^{descrizione}"
                          :immediate-finish t :empty-lines-before 1)
                         ("k" "stack" entry (file "roba/facendo.org")
                          "* %^{interrotto}  %^g\n  prempted: %K at %T\n  :orologio:\n:END:\n" :clock-in t :immediate-finish t :empty-lines-before 1)
                         ("s" "secchiata" entry (file "roba/secchiata.org")
                          "* %^{item} %^g\n  %^{data}" :immediate-finish t :clock-resume t
                          :empty-lines-before 1)
                         ("i" "incollati" entry (file "ciaparme/incollati.org")
                          "* %^{descrizione}\n\n  %x" :immediate-finish t :clock-resume t
                          :kill-buffer :empty-lines-before 1)
                         ("r" "rae" entry (file "ciaparme/consultare.org")
                          "* [[http://buscon.rae.es/drae/?type=3&val=%x][%x]]"
                          :immediate-finish t :empty-lines-before 1 :clock-resume t
                          :kill-buffer)
                         ("e" "enes" entry (file "ciaparme/translate.org")
                          "* [[http://www.wordreference.com/es/translation.asp?tranword=%x][%x]]" :empty-lines-before 1 :immediate-finish t :clock-resume t :kill-buffer)
                         ("l" "lessico" entry (file "ciaparme/lessico.org")
                          "* %^{descrizione}\n\n  %x" :immediate-finish t :clock-resume t
                          :kill-buffer :empty-lines-before 1)
                         )
 org-startup-indented t
 org-after-todo-state-change-hook '(org-clock-out-if-current)
 org-from-is-user-regexp "\\<humberto\\.nanni@gmail\\.com\\>\\|\\<Humberto Nanni Hernández\\>"
 org-src-mode-hook '(org-src-babel-configure-edit-buffer org-src-mode-configure-edit-buffer)
 org-agenda-before-write-hook '(org-agenda-add-entry-text)
 org-babel-pre-tangle-hook '(save-buffer)
 org-font-lock-set-keywords-hook '(org-drill-add-cloze-fontification)
 org-global-properties '(("STYLE_ALL" . "habit"))
 org-drill-maximum-duration 5
 org-mode-hook '((lambda nil
                  (setq prettify-symbols-alist
                   (cons (quote ("*" . 8990)) prettify-symbols-alist))
                  (setq prettify-symbols-alist
                   (cons (quote ("**" . 8990)) prettify-symbols-alist))
                  (setq prettify-symbols-alist
                   (cons (quote ("***" . 8990)) prettify-symbols-alist))
                  (setq prettify-symbols-alist
                   (cons (quote ("****" . 8990)) prettify-symbols-alist))
                  (setq prettify-symbols-alist
                   (cons (quote ("*****" . 8990)) prettify-symbols-alist))
                  (setq prettify-symbols-alist
                   (cons (quote ("******" . 8990)) prettify-symbols-alist))
                  (setq prettify-symbols-alist
                   (cons (quote ("*******" . 8990)) prettify-symbols-alist))
                  (setq prettify-symbols-alist
                   (cons (quote ("********" . 8990)) prettify-symbols-alist))
                  (setq prettify-symbols-alist
                   (cons (quote ("*********" . 8990)) prettify-symbols-alist))
                  (setq prettify-symbols-alist
                   (cons (quote ("**********" . 8990)) prettify-symbols-alist))
                  (setq prettify-symbols-alist
                   (cons (quote ("***********" . 8990)) prettify-symbols-alist))
                  (setq prettify-symbols-alist
                   (cons (quote ("TODO" . 8801)) prettify-symbols-alist))
                  (setq prettify-symbols-alist
                   (cons (quote ("SOMEDAY" . 8609)) prettify-symbols-alist))
                  (setq prettify-symbols-alist
                   (cons (quote ("DONE" . 10004)) prettify-symbols-alist))
                  (setq prettify-symbols-alist
                   (cons (quote ("STARTED" . 8607)) prettify-symbols-alist))
                  (setq prettify-symbols-alist
                   (cons (quote ("SCHEDULED" . 9735)) prettify-symbols-alist))
                  (setq prettify-symbols-alist
                   (cons (quote ("DEADLINE" . 8740)) prettify-symbols-alist))
                  (setq prettify-symbols-alist
                   (cons (quote ("PROPERTIES" . 9799)) prettify-symbols-alist))
                  (setq prettify-symbols-alist
                   (cons (quote ("logbook" . 9801)) prettify-symbols-alist))
                  (setq prettify-symbols-alist
                   (cons (quote ("END" . 9666)) prettify-symbols-alist))
                  )
                 #[0 "\300\301\302\303\304$\207"
                   [add-hook change-major-mode-hook org-show-block-all append local] 5
                   "\n\n(fn)"]
                 #[nil "\300\301\302\303\304$\207"
                   [add-hook change-major-mode-hook org-babel-show-result-all append local]
                   5]
                 org-babel-result-hide-spec org-babel-hide-all-hashes)
 org-refile-targets '((org-agenda-files :maxlevel . 5) (nil :maxlevel . 5))
 org-todo-state-tags-triggers '(("CANCELLED" ("cancelled" . t))
                                ("WAITING" ("waiting" . t) ("next"))
                                ("SOMEDAY" ("waiting" . t)) (done ("waiting") ("next"))
                                ("TODO" ("waiting") ("cancelled") ("next"))
                                ("STARTED" ("waiting"))
                                ("DONE" ("waiting") ("cancelled") ("next")))
 org-archive-hook '(org-attach-archive-delete-maybe)
 org-use-speed-commands t
 org-clock-persist 'history
 org-ctrl-c-ctrl-c-hook '(org-babel-hash-at-point org-babel-execute-safely-maybe)
 org-refile-use-outline-path 'file
 org-clock-auto-clock-resolution nil
 org-clock-in-switch-to-state "STARTED"
 org-directory "~/roba/vicenda/orgs/"
 org-enforce-todo-dependencies t
 org-cycle-hook '(org-cycle-hide-archived-subtrees org-cycle-hide-drawers
                  org-cycle-show-empty-lines org-optimize-window-after-visibility-change)
 org-archive-location "::* archived"
 org-babel-python-command "python -i ~/.pythonrc.py"
 org-habit-today-glyph 948
 org-enforce-todo-checkbox-dependencies t
 org-ditaa-eps-jar-path "/usr/share/emacs/site-lisp/contrib/scripts/DitaaEps.jar"
 org-refile-allow-creating-parent-nodes 'confirm
 org-todo-keywords '((sequence "TODO(t)" "STARTED(s)" "|" "DONE(d!)")
                     (sequence "WAITING(w@)" "STARTED(s)" "|" "DELEGATED(D@)" "SOMEDAY(S@)"
                      "CANCELLED(C@)")
                     )
 org-modules '(org-bbdb org-gnus org-id org-habit org-w3m)
 org-agenda-window-setup 'current-window
 org-agenda-span 'day
 org-deadline-warning-days 0
 org-babel-tangle-lang-exts '(("ruby" . "rb") ("python" . "py") ("emacs-lisp" . "el")
                              ("elisp" . "el"))
 org-confirm-elisp-link-function 'yes-or-no-p
 org-metadown-hook '(org-babel-pop-to-session-maybe)
 org-log-into-drawer "logbook"
 org-ditaa-jar-path "/home/robaccia/roba/vicenda/sources/org/org-mode/contrib/scripts/ditaa.jar"
 org-blocker-hook '(org-block-todo-from-checkboxes
                    org-block-todo-from-children-or-siblings-or-parent)
 org-cycle-separator-lines 1
 org-drill-maximum-items-per-session 10
 org-babel-load-languages '((shell . t) (python . t) (ditaa . t) (dot . t) (octave . t)
                            (sqlite . t) (ruby . t))
 org-agenda-files '("~/roba/vicenda/orgs/agendables/abito.org"
                    "~/roba/vicenda/orgs/agendables/facendo.org"
                    "~/roba/vicenda/orgs/agendables/progetti.org"
                    "~/roba/vicenda/orgs/agendables/secchiata.org")
 org-clock-out-hook '(org-clock-remove-empty-clock-drawer)
 org-confirm-babel-evaluate nil
 org-clock-out-remove-zero-time-clocks t
 org-after-todo-statistics-hook '(org-summary-todo)
 org-tag-alist '((:startgroup) ("@cubicolo" . 99) ("@lab" . 108) ("@casa" . 97)
                 ("@room" . 114) (:endgroup) (:startgroup) ("refile" . 114) (:endgroup)
                 (:startgroup) ("waiting" . 119) ("started" . 115) ("verify" . 118)
                 ("delegated" . 100) ("someday" . 109) ("cancelled" . 99) (:endgroup)
                 (:startgroup) ("sospeso" . 115) ("interrotto" . 105) (:endgroup)
                 ("citazioni" . 122))
 )