Exit NVDA safely by closing all top level windows (#12183)
Unreleased silent installs of NVDA were causing a crash at the end of the install process.
it was found NVDA closes the wxApp by forcibly exiting the MainLoop. This is not recommended and the behaviour of closing the TopWindow is recommended.
NVDA now will exit even with windows still open, the exit process now closes all NVDA windows and dialogs
