ims_qos: check and log for NULL sessionId

(cherry picked from commit 1b29131)

src/modules/ims_qos/rx_aar.c

@@ -149,6 +149,11 @@ void async_aar_callback(int is_timeout, void *param, AAAMessage *aaa, long elaps
         LM_DBG("Success, received code: [%i] from PCRF for AAR request\n", cdp_result);
         counter_inc(ims_qos_cnts_h.successful_media_aars);
 
+	if(!aaa->sessionId) {
+            LM_ERR("NULL AAA sessionId from PCRF!\n");
+            goto error;
+        }
+
         LM_DBG("Auth session ID [%.*s]", aaa->sessionId->data.len, aaa->sessionId->data.s);
 
 	if(!data->aar_update) {
@@ -286,6 +291,12 @@ void async_aar_reg_callback(int is_timeout, void *param, AAAMessage *aaa, long e
             create_return_code(result);
             goto done;
         }
+
+	if(!aaa->sessionId) {
+            LM_ERR("NULL AAA sessionId from PCRF!\n");
+            goto error;
+        }
+
         //need to set Rx auth data to say this session has been successfully opened
         //This is used elsewhere to prevent acting on termination events when the session has not been opened
         //getting auth session