bug#51794: 29.0.50; invalid input events generated from a mouse click for the tab bar

[Eli Zaretskii]

> From: Mark Kennedy <mark.t.kennedy@gmail.com>
> Date: Thu, 18 Nov 2021 18:39:23 -0500
> Cc: 51794@debbugs.gnu.org
> 
> bug fix #50993 is the bug.  it made make_lispy_position skip setting
> posn to the tab_bar if track_mouse is non-nil.  why track_mouse is nil
> for some frames and not for others i didn't look into.
> thoughts/comments?

Please do look into that last part, because we need to understand the
situations in which this happens well enough to devise a solution.  We
don't want to revert that fix because it will re-introduce a larger
problem.  Specifically, why does this happen to you only under those
customizations and not in "emacs -Q"?

Martin, any suggestions?