disposable UI; loading screen mockup (i heard like loading screen -- sonic 06)

src/net/torvald/terrarum/ui/UIPieMenu.kt

@@ -118,4 +118,7 @@ class UIPieMenu : UICanvas {
         UICanvas.endClosingFade(handler)
         handler!!.scale = 1f
     }
+
+    override fun dispose() {
+    }
 }