bug#12251: 24.2.50; crash in note_mouse_highlight

[martin rudalics]

>>  >> "#<window 139> is not a valid window"
>>
>> The above means that we've been running Lisp code on a dead window and
>> that call was rejected with an error by `window-normalize-window'.  If
>> this happens during a call from C, we have a problem.
>
> I don't think this error was thrown from C.

The error was obviously thrown from Lisp which per se is harmless.  But
I'm quite convinced that it was thrown by a Lisp function directly or
indirectly called from C.

> Most probably, it was
> thrown from Lisp, but since that unwinds the stack, there's no Lisp
> backtrace that could confirm that.

How could we explain a crash if it's all within Lisp code?

> I guess we need more checks in the mouse-highlight code, to account
> for such cases.

Is note_mouse_highlight all we have to look at?

martin