prevent crash when using WM close button on "new route name contains bad chars" dialog.

prevent crash when using WM close button on "new route name contains bad chars" dialog.

The dialog would be created twice, once because the user hit enter etc. to indicate they were done editing,
and once because focus left the name text entry, also indicate the end of editing. We now note that we're
already processing the end of a name edit, and do nothing in that case