Creator does not notice file updates when in Options dialog

1. Open a file in Creator.
2. Open the Options dialog using "File" -> "Options...".
3. Edit and save the file from step 1 using an external editor, e.g. gedit.
4. Give focus to the Options dialog.
   Creator won't report the changed file.
5. Click "Cancel" to close the Options dialog.
   Creator won't report the changed file.
6. Give focus to a different application, e.g. a terminal window.
7. Give focus to Creator
   The file changed indeed. Creator shows the "File Changed" dialog at last.

Creator should show the "File Changed" dialog after closing the Options dialog. I think this is a serious issue because it may lead to unnoticed loss of data. On Windows, this seems to work correctly.

Found while preparing an update for Squish test tst_edit_externally.