UI: Disable properties for groups in context menu

Makes it consistent with the source context menu.

UI/window-basic-main.cpp

@@ -5422,8 +5422,10 @@ void OBSBasic::CreateSourcePopupMenu(int idx, bool preview)
 				   OBS_SOURCE_INTERACTION);
 
 		popup.addAction(QTStr("Filters"), this, SLOT(OpenFilters()));
-		popup.addAction(QTStr("Properties"), this,
-				SLOT(on_actionSourceProperties_triggered()));
+		action = popup.addAction(
+			QTStr("Properties"), this,
+			SLOT(on_actionSourceProperties_triggered()));
+		action->setEnabled(obs_source_configurable(source));
 	}
 
 	popup.exec(QCursor::pos());