bug#3192: 23.0.92; disabling tooltip-mode inhibits showing Customize error msgs

[Mauro Aranda]

I'm able to reproduce with Emacs 26.2 on Windows, but not on GNU/Linux.

When tooltip-mode is disabled, show-help-function is set to
tooltip-show-help-non-mode.  When this function is called with nil as the
HELP argument, it may clear the echo area.  But my analysis is that it is being
called at two different times:

On GNU/Linux, it is called right after the click in the button (in this case,
the State button).  So, the echo area is cleared.  Then, clicking in the
"Set for Current Session" item, triggers the error and then the error message
is displayed.  tooltip-show-help-non-mode is not called after that,
so no cleaning happens.

But on Windows, it is not called right after the click in the State button,
rather it is called (with a nil argument) after the click in the item
"Set for Current Session", which results in cleaning the echo area.  That,
in fact, is what clears the error message.

It is possible to workaround this problem in tooltip-show-help-non-mode, but
I would like to know if that is desirable, or other approach is preferred.
Also, I don't know what happens on other systems other than GNU/Linux and
Windows, so it would be good to have that information.

Best regards,
Mauro.