[fix] Ensure fatal panics are notified

Due to a bug in the existing `notifier.NotifySync` method, we end up
using the notifier's config value to determine whether to send
synchronously or async. In the case of a fatal panic (i.e not
`AutoNotified` or `Recover`-ed) it still got sent asynchronously.
This change ensures that it does get sent synchronously.

panicwrap.go

@@ -22,7 +22,7 @@ func defaultPanicHandler() {
 			defaultNotifier.Config.logf("bugsnag.handleUncaughtPanic: %v", err)
 		}
 		state := HandledState{SeverityReasonUnhandledPanic, SeverityError, true, ""}
-		Notify(toNotify, state, Configuration{Synchronous: true})
+		defaultNotifier.NotifySync(toNotify, true, state)
 	})
 
 	if err != nil {