A blind transfer to the parking thread would cause a segfault because copy_request accesses dst->data w/o being able to tell whether it is proerly initialized

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@146970 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -16282,7 +16282,7 @@ static void *sip_park_thread(void *stuff)
 {
 	struct ast_channel *transferee, *transferer;	/* Chan1: The transferee, Chan2: The transferer */
 	struct sip_dual *d;
-	struct sip_request req;
+	struct sip_request req = {0,};
 	int ext;
 	int res;