bug#60692: 29.0.60; current-indentation wrong without outline ellipsis

[Juri Linkov]

When there is an outline ellipsis displayed at the end of outline headings,
then the correct indentation 2 is returned in this test case:

(progn
  (switch-to-buffer (get-buffer-create "test1"))
  (insert "* h\n  .\n")
  (outline-mode)
  (outline-hide-sublevels 1)
  (goto-char 8)
  (current-indentation))

But when the ellipsis is disabled with invisibility-spec:

(progn
  (switch-to-buffer (get-buffer-create "test2"))
  (insert "* h\n  .\n")
  (outline-mode)
  (remove-from-invisibility-spec '(outline . t))
  (add-to-invisibility-spec 'outline)
  (outline-hide-sublevels 1)
  (goto-char 8)
  (current-indentation))

then the returned indentation is 0 that is incorrect.