refactor: remove unused 'virtual' keywords

src/graphics/ui/elements/UINode.hpp

@@ -225,11 +225,11 @@ namespace gui {
         virtual glm::vec2 calcPos() const;
         virtual void setPos(glm::vec2 pos);
         virtual glm::vec2 getPos() const;
-        virtual glm::vec2 getSize() const;
+        glm::vec2 getSize() const;
         virtual void setSize(glm::vec2 size);
-        virtual glm::vec2 getMinSize() const;
+        glm::vec2 getMinSize() const;
         virtual void setMinSize(glm::vec2 size);
-        virtual glm::vec2 getMaxSize() const;
+        glm::vec2 getMaxSize() const;
         virtual void setMaxSize(glm::vec2 size);
         /// @brief Called in containers when new element added
         virtual void refresh() {};

src/graphics/ui/gui_util.hpp

@@ -3,12 +3,16 @@
 #include <memory>
 #include <string>
 
-#include "GUI.hpp"
 #include "delegates.hpp"
 #include "typedefs.hpp"
 
 class Engine;
 
+namespace gui {
+    class GUI;
+    class UINode;
+}
+
 namespace guiutil {
     /// @brief Create element from XML
     /// @param source XML