🐛 Connect callbacks on Slider UIObject

pandora/game_objects/ui_objects/Slider.js

@@ -7,5 +7,7 @@ class Slider extends UIObject
         this.setPosition(0, 0);
         this.setSize(200, 25);
         this.setStyle(DEFAULT_STYLE);
+
+        this.connectCallbacks();
     }
 }