message: Guard just a tiny bit
diff: @@ -168,7 +168,7 @@ function ItemService(): ItemServiceType {
  )
  : [];
  // moveAmount could be more than maxStackSize if there is more than one stack on a character!
  - const moveAmount = amount || item.amount;
  + const moveAmount = amount || item.amount || 1;
  let addAmount = moveAmount;
  let removeAmount = moveAmount;
  let removedSourceItem = false;
  