Don't send idle events to the windows about to be destroyed.

Don't send idle events to the windows about to be destroyed.

This is useless and can apparently result in some problems as of r25877 and
r25877 (from 8 years ago) added explicit checks preventing processing such
events in wxToolBar and wxMenu. Instead, simply don't generate these events in
the first place and also remove the now unnecessary checks for them.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70179 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775