[SettingsButtonWidget] Fix memory leak from unparented popup (#7055)

cockatrice/src/interface/widgets/quick_settings/settings_button_widget.cpp

@@ -20,6 +20,13 @@ SettingsButtonWidget::SettingsButtonWidget(QWidget *parent)
     setLayout(layout);
 }
 
+SettingsButtonWidget::~SettingsButtonWidget()
+{
+    // We don't parent the popup because it might lead to better behavior on certain window managers.
+    // So we have to manually delete it
+    popup->deleteLater();
+}
+
 void SettingsButtonWidget::addSettingsWidget(QWidget *toAdd) const
 {
     popup->addSettingsWidget(toAdd);

cockatrice/src/interface/widgets/quick_settings/settings_button_widget.h

@@ -19,6 +19,9 @@ class SettingsButtonWidget : public QWidget
 
 public:
     explicit SettingsButtonWidget(QWidget *parent = nullptr);
+
+    ~SettingsButtonWidget() override;
+
     void addSettingsWidget(QWidget *toAdd) const;
     void removeSettingsWidget(QWidget *toRemove) const;
     void setButtonIcon(QPixmap iconMap);