b simulator + websocket

simulator changed_UI_items returning null instead of {}
cleanup of process broadcast discard on empty update

tools/simulators.cpp

@@ -85,11 +85,11 @@ json Simulators::changed_UI_items()
 {
     if (this->m_simulators.empty())
     {
-        return json();
+        return "{}"_json;
     }
     if (this->m_current_simulator.empty())
     {
-        return json();
+        return "{}"_json;
     }
 
     json after = this->m_simulators.at(m_current_simulator)->get_UI_items();

tools/websocket.cpp

@@ -127,7 +127,10 @@ void Websocket::process_broadcast()
             }
         }
         std::string update = m_on_update();
-        if (!update.empty() && update != "{}")
+        if (update.empty() || update == "{}")
+        {
+            continue;
+        }
         {
             std::lock_guard<std::mutex> guard(m_connection_lock);
             for (auto it = m_connections.begin(); it != m_connections.end(); ++it) {