fix an issue with statuscode verification uncovered by cppcheck

src/server/ua_services_subscription.c

@@ -141,7 +141,7 @@ Service_CreateMonitoredItems_single(UA_Server *server, UA_Session *session, UA_S
     Service_Read_single(server, session, timestampsToReturn, &request->itemToMonitor, &v);
 
     /* Allow return codes "good" and "uncertain" */
-    if((v.hasStatus >> 30) > 1) {
+    if(v.hasStatus && (v.status >> 30) > 1) {
         result->statusCode = v.status;
         UA_DataValue_deleteMembers(&v);
         return;