/ fixes possibility for accessing of struct when null

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@5896 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_vpb.c

@@ -1149,10 +1149,15 @@ static inline int monitor_handle_notowned(struct vpb_pvt *p, VPB_EVENT *e)
 				}
 			} else if (e->data == p->ring_timer_id) {
 				/* We didnt get another ring in time! */
+				if (p->owner){
 					if (p->owner->_state != AST_STATE_UP)  {
 						 /* Assume caller has hung up */
 						vpb_timer_stop(p->ring_timer);
 					}
+				} else {
+					 /* No owner any more, Assume caller has hung up */
+					vpb_timer_stop(p->ring_timer);
+				}
 			} 
 			break;