LibGUI: Calculate Window min_size on show

Author: https://github.com/frhun
Commit: 80ea141ffe
Pull-request: https://github.com/SerenityOS/serenity/pull/14478
Issue: https://github.com/SerenityOS/serenity/issues/14420

Userland/Libraries/LibGUI/Window.h

@@ -231,6 +231,8 @@ protected:
     virtual void leave_event(Core::Event&);
 
 private:
+    void update_min_size();
+
     void update_cursor();
     void focus_a_widget_if_possible(FocusSource);