Bug: org-clock-cancel doesn't set org-clock-current-task correctly [9.2.3 (9.2.3-23-g967801-elpaplus @ <snip>/.emacs.d/elpa/26.2/develop/org-plus-contrib-20190603/)]

[Aaron Zeng <me@bcc32.com>]

(I'm running org mode from the Spacemacs org layer, which includes the
org-plus-contrib package).

Reproduction:
1. Create a new entry "* TODO Temp"
2. Clock in under that entry
3. Cancel the clock
4. [M-x describe-variable org-clock-current-task] is still set to
"Temp" instead of being nil, which is what I expected.
5. In Spacemacs with the spaceline-all-the-icons mode line, "Temp"
still appears in the "currently clocked task" position.

Emacs  : GNU Emacs 26.2 (build 1, x86_64-w64-mingw32)
 of 2019-04-13
Package: Org mode version 9.2.3 (9.2.3-23-g967801-elpaplus @
<snip>/.emacs.d/elpa/26.2/develop/org-plus-contrib-20190603/)

current state:
==============
(setq
 org-src-mode-hook '(org-src-babel-configure-edit-buffer
org-src-mode-configure-edit-buffer)
 org-babel-after-execute-hook '(spacemacs/ob-fix-inline-images)
 org-insert-heading-respect-content t
 org-metadown-hook '(org-babel-pop-to-session-maybe)
 org-agenda-tags-todo-honor-ignore-options t
 org-clock-out-hook '(org-clock-remove-empty-clock-drawer)
 org-refile-targets '((nil :maxlevel . 10) (org-agenda-files :maxlevel . 10))
 org-src-tab-acts-natively t
 org-imenu-depth 8
 org-download-annotate-function 'org-download-annotate-default
 org-mode-hook '(org-clock-load #[0 "\301\211 \207"
[imenu-create-index-function org-imenu-get-tree] 2] #[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
spacemacs/org-setup-evil-surround spacemacs/load-yasnippet
toc-org-enable
                 org-download-enable org-bullets-mode
dotspacemacs//prettify-spacemacs-docs
spacemacs//org-babel-do-load-languages spacemacs//evil-org-mode
org-eldoc-load spacemacs//init-company-org-mode company-mode)
 org-clock-persist t
 org-outline-path-complete-in-steps nil
 org-archive-hook '(org-attach-archive-delete-maybe)
 org-agenda-restore-windows-after-quit t
 org-confirm-elisp-link-function 'yes-or-no-p
 org-startup-indented t
 org-startup-with-inline-images t
 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-babel-load-languages '((shell . t) (python . t) (perl . t) (sql .
t) (C . t) (emacs-lisp . t))
 org-log-done 'time
 org-export-backends '(ascii html icalendar latex org texinfo)
 org-src-lang-modes '(("arduino" . arduino) ("redis" . redis) ("php" .
php) ("C" . c) ("C++" . c++) ("asymptote" . asy) ("bash" . sh)
("beamer" . latex) ("calc" . fundamental) ("cpp" . c++) ("ditaa" .
artist) ("dot" . fundamental) ("elisp" . emacs-lisp)
                      ("ocaml" . tuareg) ("screen" . shell-script)
("shell" . sh) ("sqlite" . sql))
 org-occur-hook '(org-first-headline-recenter)
 org-log-into-drawer t
 org-agenda-todo-ignore-time-comparison-use-seconds t
 org-ctrl-c-ctrl-c-hook '(spacemacs//counsel-org-ctrl-c-ctrl-c-org-tag)
 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-babel-tangle-lang-exts '(("D" . "d") ("C++" . "cpp") ("perl" .
"pl") ("python" . "py") ("emacs-lisp" . "el") ("elisp" . "el"))
 org-refile-use-outline-path 'file
 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")
                       ("orgit-rev" :store orgit-rev-store :follow
orgit-rev-open :export orgit-rev-export :complete
orgit-rev-complete-link) ("orgit-log" :store orgit-log-store :follow
orgit-log-open :export orgit-log-export :complete
orgit-log-complete-link)
                       ("orgit" :store orgit-status-store :follow
orgit-status-open :export orgit-status-export :complete
orgit-status-complete-link) ("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-present-mode-hook '(spacemacs//org-present-start)
 org-capture-templates '(("t" "Todo" entry (file "") "* TODO %?\n%U\n%a"))
 org-link-translation-function 'toc-org-unhrefify
 org-image-actual-width nil
 org-present-mode-quit-hook '(spacemacs//org-present-end)
 org-directory "~/org/default"
 org-download-abbreviate-filename-function 'file-relative-name
 org-agenda-todo-ignore-scheduled 'future
 org-default-notes-file "~/org/default/refile.org"
 )