Don't exit event loop when exception occurs inside Yield().

If an unhandled exception occurs in an event handler called from Yield(),
don't exit the current event loop which can continue running after handling
this exception in the code calling Yield().

Closes #16419.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@77075 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775