Add missing override

Author: Flamefire

libs/s25main/controls/ctrlImage.h

@@ -18,7 +18,7 @@ class ctrlImage : public Window, public ctrlBaseTooltip, public ctrlBaseImage
     ~ctrlImage() override;
 
     bool Msg_MouseMove(const MouseCoords& mc) override;
-    Rect GetBoundaryRect() const;
+    Rect GetBoundaryRect() const override;
 
 protected:
     void Draw_() override;