Bug: clocktable error in org-agenda [9.2.2 (release_9.2.2-245-g9d7b1e @ /home/dortmann/src/git-org-mode/lisp/)]

[Daniel Ortmann <daniel.ortmann@oracle.com>]

Remember to cover the basics, that is, what you expected to happen and
what in fact did happen.  You don't know how to make a good report?  See

     https://orgmode.org/manual/Feedback.html#Feedback

Your bug report will be posted to the Org mailing list.
------------------------------------------------------------------------

Since this problem has been occurring for a few months now, it's got to
be something wrong in my configuration.

In the org agenda, pressing R activates the clock report but pressing it
again does not turn it off.  The same behavior occurs through the menu;
clicking the view clock report checkbox turns the checkbox on and the
clock report appears in the agenda ... but clicking it again does not
turn the clock report off; it stays visible.

To log the bug report I started with
emacs -Q -l ~/minimal-org.el
then ran M-x org-agenda followed by a and then R.
The following debug trace immediately occurred.

Please clue in the clueless.
Thank you!

Debugger entered--Lisp error: (wrong-type-argument stringp nil)
  file-exists-p(nil)
  org-check-agenda-file(nil)
  org-agenda-prepare-buffers((nil))
  org-dblock-write:clocktable((:name "clocktable" :link t :maxlevel 2
:tstart 737122 :tend 737123 :scope agenda :indentation-column 0 :content
"\n"))
  org-update-dblock()
  org-clock-get-clocktable(:link t :maxlevel 2 :tstart 737122 :tend
737123 :scope agenda)
  apply(org-clock-get-clocktable (:link t :maxlevel 2 :tstart 737122
:tend 737123 :scope agenda))
  org-agenda-list(nil 737122 day nil)
  (let nil (org-agenda-list 'nil 737122 'day nil))
  eval((let nil (org-agenda-list 'nil 737122 'day nil)))
  org-let(nil (org-agenda-list 'nil 737122 'day nil))
  org-agenda-redo()
  org-agenda-clockreport-mode()
  funcall-interactively(org-agenda-clockreport-mode)
  call-interactively(org-agenda-clockreport-mode nil nil)
  command-execute(org-agenda-clockreport-mode)


Emacs  : GNU Emacs 27.0.50 (build 3, x86_64-pc-linux-gnu, X toolkit,
Xaw3d scroll bars)
 of 2019-03-04
Package: Org mode version 9.2.2 (release_9.2.2-245-g9d7b1e @
/home/dortmann/src/git-org-mode/lisp/)

current state:
==============
(setq
 org-src-mode-hook '(org-src-babel-configure-edit-buffer
             org-src-mode-configure-edit-buffer)
 org-metadown-hook '(org-babel-pop-to-session-maybe)
 org-clock-out-hook '(org-clock-remove-empty-clock-drawer)
 org-mode-hook '(#[0 "\300\301\302\303\304$\207"
           [add-hook change-major-mode-hook org-show-all append local]
           5]
         #[0 "\300\301\302\303\304$\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-archive-hook '(org-attach-archive-delete-maybe)
 org-confirm-elisp-link-function 'yes-or-no-p
 org-agenda-before-write-hook '(org-agenda-add-entry-text)
 org-metaup-hook '(org-babel-load-in-session-maybe)
 org-bibtex-headline-format-function #[257 "\300\236A\207" [:title] 3
"\n\n(fn ENTRY)"]
 org-babel-pre-tangle-hook '(save-buffer)
 org-tab-first-hook '(org-babel-hide-result-toggle-maybe
              org-babel-header-arg-expand)
 org-occur-hook '(org-first-headline-recenter)
 org-cycle-hook '(org-cycle-hide-archived-subtrees
org-cycle-show-empty-lines
          org-optimize-window-after-visibility-change)
 org-speed-command-hook '(org-speed-command-activate
              org-babel-speed-command-activate)
 org-dynamic-block-alist '(("columnview" . org-columns-insert-dblock)
               ("clocktable" . org-clock-report))
 org-confirm-shell-link-function 'yes-or-no-p
 org-link-parameters '(("id" :follow org-id-open)
               ("eww" :follow eww :store org-eww-store-link)
               ("rmail" :follow org-rmail-open :store
            org-rmail-store-link)
               ("mhe" :follow org-mhe-open :store org-mhe-store-link)
               ("irc" :follow org-irc-visit :store org-irc-store-link
            :export org-irc-export)
               ("info" :follow org-info-open :export org-info-export
            :store org-info-store-link)
               ("gnus" :follow org-gnus-open :store org-gnus-store-link)
               ("docview" :follow org-docview-open :export
            org-docview-export :store org-docview-store-link)
               ("bibtex" :follow org-bibtex-open :store
            org-bibtex-store-link)
               ("bbdb" :follow org-bbdb-open :export org-bbdb-export
            :complete org-bbdb-complete-link :store
            org-bbdb-store-link)
               ("w3m" :store org-w3m-store-link) ("file+sys")
               ("file+emacs") ("doi" :follow org--open-doi-link)
               ("elisp" :follow org--open-elisp-link)
               ("file" :complete org-file-complete-link)
               ("ftp" :follow
            (lambda (path) (browse-url (concat "ftp:" path))))
               ("help" :follow org--open-help-link)
               ("http" :follow
            (lambda (path) (browse-url (concat "http:" path))))
               ("https" :follow
            (lambda (path) (browse-url (concat "https:" path))))
               ("mailto" :follow
            (lambda (path) (browse-url (concat "mailto:" path))))
               ("news" :follow
            (lambda (path) (browse-url (concat "news:" path))))
               ("shell" :follow org--open-shell-link))
 org-agenda-start-on-weekday nil
 )