res_stasis: Fix crash when handling a failed blind transfer message.

This changes fixes a crash that occurs when stasis determines if it
should send a message out to an application or not. The code
incorrectly assumed that a bridge snapshot would always be present
when in reality for failure cases it may not be.

ASTERISK-23573 #close
........

Merged revisions 412882 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@412883 65c4cc65-6c06-0410-ace0-fbb531ad65f3

res/stasis/app.c

@@ -649,7 +649,7 @@ static void bridge_blind_transfer_handler(void *data, struct stasis_subscription
 	struct ast_bridge_blob *blob = stasis_message_data(message);
 
 	if (bridge_app_subscribed(app, blob->channel->uniqueid) ||
-		bridge_app_subscribed_involved(app, blob->bridge)) {
+		(blob->bridge && bridge_app_subscribed_involved(app, blob->bridge))) {
 		stasis_publish(app->topic, message);
 	}
 }