Open [[file+emacs:file::options]] links

* lisp/org.el (org-open-at-point): Allow options when using
  applications in links with options.
(org-open-file-with-system, org-open-file-with-emacs): Change
signature to be compatible with `org-open-file'
org-element: Add checks relative to cache

* lisp/org-element.el (org-element--cache-put, org-element-context):
  Check if cache is active before trying to access it.
org-element: Fix parsing of inlinetasks within lists

* lisp/org-element.el (org-element--list-struct): Fix regexp.
Merge branch 'maint'
org-bibtex: Fix `org-bibtex-read' on an empty field

* lisp/org-bibtex.el (org-bibtex-read): Check string length before
  using aref.

If a field in a bibtex entry is empty:

@article(test,
   description = "")

the function org-bibtex-read throws an exception because of
using aref on this empty string.

The solution is to check the length of the string before.

TINYCHANGE

Signed-off-by: Stefan-W. Hahn <stefan.hahn@s-hahn.de>
Merge branch 'maint'