doing <flash> *0 while on fxs causes Asterisk to crash (bug 2963)

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/v1-0@4376 65c4cc65-6c06-0410-ace0-fbb531ad65f3

CHANGES

@@ -1,5 +1,7 @@
+ -- chan_zap
+    -- seg fault fix
  -- rtp
-    -- fix for a seg fault
+    -- seg fault fix
  -- chan_sip
     -- fix to prevent seg fault when attempting a transfer
     -- fix bug with supervised transfers

channels/chan_zap.c

@@ -5039,9 +5039,11 @@ static void *ss_thread(void *data)
 					p->subs[SUB_THREEWAY].owner;
 				struct zt_pvt *pbridge = NULL;
 				  /* set up the private struct of the bridged one, if any */
-				if (nbridge && nbridge->bridge) pbridge = nbridge->bridge->pvt->pvt;
-				if (nbridge && 
-				    (!strcmp(nbridge->type,"Zap")) &&
+				if (nbridge && nbridge->bridge) 
+					pbridge = nbridge->bridge->pvt->pvt;
+				if (nbridge && pbridge && 
+				    (!strcmp(nbridge->type,"Zap")) && 
+					(!strcmp(nbridge->bridge->type, "Zap")) &&
 				    ISTRUNK(pbridge)) {
 					int func = ZT_FLASH;
 					/* Clear out the dial buffer */