Fixed AboutDialog leaking (#1168)

src/MainWindow.cpp

@@ -913,6 +913,7 @@ void MainWindow::on_actionTabs_triggered()
 void MainWindow::on_actionAbout_triggered()
 {
     AboutDialog *a = new AboutDialog(this);
+    a->setAttribute(Qt::WA_DeleteOnClose);
     a->open();
 }
 

src/dialogs/NewFileDialog.cpp

@@ -165,6 +165,7 @@ void NewFileDialog::on_projectsListWidget_itemDoubleClicked(QListWidgetItem *ite
 void NewFileDialog::on_aboutButton_clicked()
 {
     AboutDialog *a = new AboutDialog(this);
+    a->setAttribute(Qt::WA_DeleteOnClose);
     a->open();
 }
 

src/dialogs/WelcomeDialog.cpp

@@ -81,6 +81,7 @@ void WelcomeDialog::onLanguageComboBox_currentIndexChanged(int index)
 void WelcomeDialog::on_checkUpdateButton_clicked()
 {
     AboutDialog *a = new AboutDialog(this);
+    a->setAttribute(Qt::WA_DeleteOnClose);
     a->open();
 }