GetBagType accepts two arguments (player and bag), in case of the vault (or Void Storage) GetBackType is called with, respectively, "playername" and "vault" as arumgents (both strings). When determining isBank, the operation bag > NUM_BAG_SLOTS compares a string with a number and throws an error.

This is introduced in commit eec50f96. Simply reverting that line to local isBank = not isVault and (bag == BANK_CONTAINER or bag > NUM_BAG_SLOTS) should solve the issue.