UI: Do not open properties dialog for groups

On initial creation of an empty group, do not open a properties dialog
for groups.

UI/window-basic-main.cpp

@@ -3983,7 +3983,7 @@ void OBSBasic::AddSource(const char *id)
 	if (id && *id) {
 		OBSBasicSourceSelect sourceSelect(this, id);
 		sourceSelect.exec();
-		if (sourceSelect.newSource)
+		if (sourceSelect.newSource && strcmp(id, "group") != 0)
 			CreatePropertiesWindow(sourceSelect.newSource);
 	}
 }