Return NULL if no CRV found

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@3180 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_zap.c

@@ -6412,6 +6412,7 @@ static struct zt_pvt *pri_find_crv(struct zt_pri *pri, int crv)
 			return p;
 		p = p->next;
 	}
+	return NULL;
 }