improve failure on unsupported browsers - catch exceptions and allow the...

improve failure on unsupported browsers - catch exceptions and allow the dialog to pop up with the 'unsupported browser' messaging.  issue #1390 and issue #1391 - NOTE: we don't go to the trouble of surpressing all errors on the console.log for unsupported browsers, as this would require patching upstream code (like node-bigint) and the errors are cosmetic, but don't prevent a clear display of what the problem is to the user.