UI: Ensure the delete of the contained widget in the UnclosableDockWidget at destruction time

src/UI/UnclosableDockWidget.cc

@@ -9,6 +9,14 @@ UnclosableDockWidget::UnclosableDockWidget(const QString &name, QWidget *parent)
     DockWidgetTitleBar::addToDock(this);
 }
 
+UnclosableDockWidget::~UnclosableDockWidget() noexcept
+{
+    QWidget *w = widget();
+    if (w != nullptr)
+        delete w;
+    setWidget(nullptr);
+}
+
 void
 UnclosableDockWidget::closeEvent(QCloseEvent *event) noexcept
 {
@@ -21,6 +29,5 @@ UnclosableDockWidget::closeEvent(QCloseEvent *event) noexcept
 void
 UnclosableDockWidget::allowClose() noexcept
 {
-    // qDebug() << "Dock" << windowTitle() << "is now allowed to be closed";
     allowedToClose = true;
 }

src/UI/UnclosableDockWidget.hh

@@ -10,6 +10,7 @@ class UnclosableDockWidget final : public QDockWidget {
 
 public:
     explicit UnclosableDockWidget(const QString &, QWidget *parent) noexcept;
+    ~UnclosableDockWidget() noexcept override;
     void allowClose() noexcept;
 
 protected: