Ref T361, better guards for plugin and sGui

No need to create an assert if plugin is not avilable, though the plugin info should be "Unspecified" in that case

src/blackgui/components/settingssimulatorcomponent.cpp

@@ -103,6 +103,7 @@ namespace BlackGui
 
         void CSettingsSimulatorComponent::setGuiValues()
         {
+            if (!sGui || !sGui->getIContextSimulator() || sGui->isShuttingDown()) { return; }
             const CInterpolationAndRenderingSetupGlobal setup = sGui->getIContextSimulator()->getInterpolationAndRenderingSetupGlobal();
 
             // time sync