fixed memory leak in EventMappingWidget

src/gui/EventMappingWidget.cxx

@@ -128,7 +128,7 @@ EventMappingWidget::EventMappingWidget(GuiObject* boss, const GUI::Font& font,
     addFocusWidget(myComboButton);
 
     VariantList combolist = instance().eventHandler().getComboList(mode);
-    myComboDialog = new ComboDialog(boss, font, combolist);
+    myComboDialog = make_unique<ComboDialog>(boss, font, combolist);
   }
 
   // Show message for currently selected event

src/gui/EventMappingWidget.hxx

@@ -90,7 +90,7 @@ class EventMappingWidget : public Widget, public CommandSender
     StringListWidget* myActionsList{nullptr};
     EditTextWidget*   myKeyMapping{nullptr};
 
-    ComboDialog* myComboDialog{nullptr};
+    unique_ptr<ComboDialog> myComboDialog;
 
     // Since this widget can be used for different collections of events,
     // we need to specify exactly which group of events we are remapping