[O] Bug: Using org-backward-paragraph in the middle of a headline produces an error [9.1.2 (9.1.2-elpaplus @ /home/omar/.emacs.d/elpa/org-plus-contrib-20171004/)]

[Omar Antolin]

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

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

Your bug report will be posted to the Org mailing list.
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It's me again, the guy that worries a lot about `org-backward-paragraph`. :)

If you have an org buffer that contains just:

    * A headline

And when the point is, say, on the `h`, you run `org-backward-paragraph`
you get the error message: "Wrong type argument: number-or-marker-p,
nil". It comes from the comparison `(>= (point) contents-end)`: when
you're in the middle of a headline, `contents-end` gets set to `nil` which
can't be compared with `(point)`.


Emacs  : GNU Emacs 24.5.1 (x86_64-pc-linux-gnu, GTK+ Version 3.18.9)
 of 2017-09-20 on lcy01-07, modified by Debian
Package: Org mode version 9.1.2 (9.1.2-elpaplus @ 
/home/omar/.emacs.d/elpa/org-plus-contrib-20171004/)

current state:
==============
(setq
 org-src-lang-modes '(("inline-js" . javascript) ("ocaml" . tuareg)
                      ("elisp" . emacs-lisp) ("ditaa" . artist)
                      ("asymptote" . asy) ("dot" . fundamental)
                      ("sqlite" . sql) ("calc" . fundamental) ("C" . c)
                      ("cpp" . c++) ("C++" . c++) ("screen" . shell-script)
                      ("shell" . sh) ("bash" . sh))
 org-tab-first-hook '(org-babel-hide-result-toggle-maybe
                      org-babel-header-arg-expand)
 org-speed-command-hook '(org-speed-command-activate
                          org-babel-speed-command-activate)
 org-occur-hook '(org-first-headline-recenter)
 org-metaup-hook '(org-babel-load-in-session-maybe)
 org-confirm-shell-link-function 'yes-or-no-p
 org-time-stamp-custom-formats '("[%a %b %d]" . "[%d/%m/%y %a %H:%M]")
 org-display-custom-times t
 org-highlight-latex-and-related '(latex script entities)
 org-support-shift-select t
 org-default-notes-file "~/Dropbox/Org/Phone/Inbox.org"
 org-after-todo-state-change-hook '(org-clock-out-if-current)
 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-mode-hook '(turn-on-org-cdlatex
                 #[0 "\300\301\302\303\304$\207"
                   [add-hook change-major-mode-hook org-show-block-all append
                    local]
                   5 "\n\n(fn)"]
                 #[0 "\300\301\302\303\304$\207"
                   [add-hook change-major-mode-hook org-babel-show-result-all
                    append local]
                   5 "\n\n(fn)"]
                 org-babel-result-hide-spec org-babel-hide-all-hashes
                 org-eldoc-load)
 org-refile-targets '((nil :maxlevel . 2) (org-agenda-files :maxlevel . 2))
 org-bibtex-headline-format-function #[257 "\300.\236A\207" [:title] 3 "\n\n(fn 
ENTRY)"]
 org-outline-path-complete-in-steps nil
 org-archive-hook '(org-attach-archive-delete-maybe)
 org-refile-use-outline-path t
 org-directory "~/Dropbox/Org"
 org-cycle-hook '(org-cycle-hide-archived-subtrees org-cycle-hide-drawers
                  org-cycle-show-empty-lines
                  org-optimize-window-after-visibility-change)
 org-refile-allow-creating-parent-nodes 'confirm
 org-link-abbrev-alist '(("wp" . "https://en.wikipedia.org/wiki/";))
 org-latex-packages-alist '(("" "amsthm" nil) "\\newtheorem{theorem}{Theorem}"
                            "\\newtheorem{proposition}{Proposition}"
                            "\\newtheorem{lemma}{Lemma}"
                            "\\newtheorem{corollary}{Corollary}"
                            
"\\theoremstyle{definition}\\newtheorem{definition}{Definition}" 
"\\theoremstyle{remark}\\newtheorem{remark}{Remark}" 
"\\newtheorem{exercise}{Exercise}")
 org-confirm-elisp-link-function 'yes-or-no-p
 org-metadown-hook '(org-babel-pop-to-session-maybe)
 org-link-parameters '(("id" :follow org-id-open)
                       ("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)
                       ("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")
                       ("cite" :follow org-bibtex-goto-citation :export nil)
                       ("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-structure-template-alist '(("s" "#+BEGIN_SRC ?\n\n#+END_SRC")
                                ("e" "#+BEGIN_EXAMPLE\n?\n#+END_EXAMPLE")
                                ("q" "#+BEGIN_QUOTE\n?\n#+END_QUOTE")
                                ("v" "#+BEGIN_VERSE\n?\n#+END_VERSE")
                                ("V" "#+BEGIN_VERBATIM\n?\n#+END_VERBATIM")
                                ("c" "#+BEGIN_CENTER\n?\n#+END_CENTER")
                                ("C" "#+BEGIN_COMMENT\n?\n#+END_COMMENT")
                                ("l" "#+BEGIN_EXPORT latex\n?\n#+END_EXPORT")
                                ("L" "#+LaTeX: ")
                                ("h" "#+BEGIN_EXPORT html\n?\n#+END_EXPORT")
                                ("H" "#+HTML: ")
                                ("a" "#+BEGIN_EXPORT ascii\n?\n#+END_EXPORT")
                                ("A" "#+ASCII: ") ("i" "#+INDEX: ?")
                                ("I" "#+INCLUDE: %file ?")
                                ("thm" "#+BEGIN_theorem\n?\n#+END_theorem")
                                ("pf" "#+BEGIN_proof\n?\n#+END_proof")
                                ("lem" "#+BEGIN_lemma\n?\n#+END_lemma")
                                ("cor" "#+BEGIN_corollary\n?\n#+END_corollary")
                                ("def"
                                 "#+BEGIN_definition\n?\n#+END_definition")
                                ("rem" "#+BEGIN_remark\n?\n#+END_remark")
                                ("exer" "#+BEGIN_exercise\n?\n#+END_exercise")
                                ("prop"
                                 "#+BEGIN_proposition\n?\n#+END_proposition")
                                )
 org-agenda-files '("~/Dropbox/Org/Phone")
 org-clock-out-hook '(org-clock-remove-empty-clock-drawer)
 org-confirm-babel-evaluate nil
 )