Prevent crash when pjsip_inv_verify_request3() return error (#4503)

Author: trengginas

pjsip/src/pjsua-lib/pjsua_call.c

@@ -1410,6 +1410,7 @@ static pj_status_t verify_request(const pjsua_call *call,
 
     if (status == PJ_SUCCESS) {
         unsigned options = 0;
+        pjsip_tx_data *tx_data_resp = NULL;
 
         /* Add SIPREC support to prevent the "bad extension" error */
         options |= PJSIP_INV_SUPPORT_SIPREC;
@@ -1418,17 +1419,20 @@ static pj_status_t verify_request(const pjsua_call *call,
         status = pjsip_inv_verify_request3(rdata,
                                            call->inv->pool_prov, &options, 
                                            offer, answer, NULL, 
-                                           pjsua_var.endpt, response);
+                                           pjsua_var.endpt, &tx_data_resp);
         if (status != PJ_SUCCESS) {
             /*
              * No we can't handle the incoming INVITE request.
              */
             pjsua_perror(THIS_FILE, "Request verification failed", status);
 
-            if (response)
-                err_code = (*response)->msg->line.status.code;
+            if (tx_data_resp)
+                err_code = tx_data_resp->msg->line.status.code;
             else
-                err_code = PJSIP_SC_NOT_ACCEPTABLE_HERE;                
+                err_code = PJSIP_SC_NOT_ACCEPTABLE_HERE;
+
+            if (response)
+                *response = tx_data_resp;
         }
     }