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

[Daniel Mendler via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

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)

Thank you!

In GNU Emacs 30.0.90 (build 1, x86_64-pc-linux-gnu, X toolkit, cairo
 version 1.18.0, Xaw scroll bars) of 2024-09-01
Windowing system distributor 'The X.Org Foundation', version 11.0.12101013
System Description: Debian GNU/Linux trixie/sid

Configured using:
 'configure --prefix=... --with-tree-sitter
 --with-native-compilation --with-x-toolkit=athena --with-dbus
 --without-selinux --without-threads --without-gsettings --without-gpm
 --with-cairo --with-cairo-xcb'

Configured features:
CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS HARFBUZZ JPEG LIBOTF LIBXML2
MODULES NATIVE_COMP NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP SOUND
SQLITE3 TIFF TOOLKIT_SCROLL_BARS TREE_SITTER WEBP X11 XDBE XIM XPM LUCID
ZLIB