bug#73050: 30.0.90; Empty tool tip when hovering over tab-bar separator

[Juri Linkov <juri@linkov.net>]

>> This is only a minor issue. After enabling `tab-bar-mode' when hovering
>> with the mouse over the `tab-bar-separator' space, an empty tool tip
>> will be shown after a short delay.
>>
>> To reproduce:
>>
>> 1. Start emacs -Q
>> 2. M-x tab-bar-mode
>> 3. Move the mouse pointer over the space right after the "*scratch*" tab
>>
>> Would it make sense to somehow prevent displaying blank tool tips, e.g.,
>> via the following advice? Or maybe blank tool tips could be prevented on
>> the tab-bar level?
>>
>> (defun x-show-tip-adv (str &rest _) (string-blank-p str))
>> (advice-add #'x-show-tip :before-until #'x-show-tip-adv)
>
> Juri, can we prevent such empty tooltips from being shown by tab bar?

Maybe this unasked-for default fallback is not needed after all:

diff --git a/src/xdisp.c b/src/xdisp.c
index f9a10267bad..18834c6b781 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -15155,8 +15155,6 @@ note_tab_bar_highlight (struct frame *f, int x, int y)
   help_echo_object = help_echo_window = Qnil;
   help_echo_pos = -1;
   help_echo_string = AREF (f->tab_bar_items, prop_idx + TAB_BAR_ITEM_HELP);
-  if (NILP (help_echo_string))
-    help_echo_string = AREF (f->tab_bar_items, prop_idx + TAB_BAR_ITEM_CAPTION);
 }
 
 #endif /* HAVE_WINDOW_SYSTEM */