Fix a crash that can occur on a transfer in chan_sip when attempting to collect

rtp stats.

(closes issue #13956)
Reported by: chris-mac
Tested by: chris-mac


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@161721 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -5556,7 +5556,7 @@ static int sip_hangup(struct ast_channel *ast)
 				if (bridge) {
 					struct sip_pvt *q = bridge->tech_pvt;
 
-					if (IS_SIP_TECH(bridge->tech) && q->rtp)
+					if (IS_SIP_TECH(bridge->tech) && q)
 						ast_rtp_set_vars(bridge, q->rtp);
 				}