inventory gamemenu visual only

src/net/torvald/terrarum/UIItemInventoryElemSimple.kt

@@ -33,6 +33,10 @@ class UIItemInventoryElemSimple(
         val drawBackOnNull: Boolean = true
 ) : UIItemInventoryCellBase(parentUI, posX, posY, item, amount, itemImage, quickslot, equippedSlot) {
 
+    // deal with the moving position
+    override var oldPosX = posX
+    override var oldPosY = posY
+
     companion object {
         val height = UIItemInventoryElem.height
     }