fix some references to the owner of a private structure that may not be present

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@148754 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -18891,7 +18891,7 @@ static int handle_request_bye(struct sip_pvt *p, struct sip_request *req)
 
 	/* Get RTCP quality before end of call */
 	if (p->do_history || p->owner) {
-		struct ast_channel *bridge = ast_bridged_channel(p->owner);
+		struct ast_channel *bridge = p->owner ? ast_bridged_channel(p->owner) : NULL;
 		char *videoqos, *textqos;
 
 		if (p->rtp) {	
@@ -18912,8 +18912,10 @@ static int handle_request_bye(struct sip_pvt *p, struct sip_request *req)
 				append_history(p, "RTCPaudioRTT", "Quality:%s", audioqos_rtt);
 			}
 			
+			if (p->owner) {
 				ast_rtp_set_vars(p->owner, p->rtp);
 			}
+		}
 
 		if (bridge) {
 			struct sip_pvt *q = bridge->tech_pvt;