set modal mode for label dailog

src/gui/edit_label_methods/editlabelmethods.cpp

@@ -36,7 +36,7 @@ EditLabelMethods::EditLabelMethods(ProjectWindow *parent):
     _project_window = parent;
     _p_label_method_str_li = new QStandardItemModel();
     ui->method_list_view->setModel(_p_label_method_str_li);
-
+this->setModal(true);
 
 #if QT_VERSION >= 0x050000
     // Qt5 code