bug#56837: 28.1.90; `current-indentation' sometimes returns zero inside invisible text

[Ihor Radchenko]

Hi,

Try to do the following:
1. emacs -Q
2. M-x outline-mode
3. Insert

* something
  a
* else

4. Move point to "* <point>something"
5. <TAB> to fold the outline
6. M-: (save-excursion (search-forward " a") (current-indentation))
   ;; => 2
7. M-: (remove-from-invisibility-spec '(outline . t))
8. M-: (add-to-invisibility-spec '(outline))
9. M-: (save-excursion (search-forward " a") (current-indentation))
   ;; => 0; expected: => 2

First reported in https://orgmode.org/list/87k0h49s7z.fsf@localhost   

Best,
Ihor