code glitch

@IBAction func purchase() {
        if let currentSelection = currentSelection{
            do{
                try vendingMachine.vend(Int(quantityStepper.value), currentSelection)
                updateDisplayWith(balance: vendingMachine.amountDeposited, totalPrice: 0, price: 0, itemQuantity: 1)
            }catch VendingMachineError.outOfStock{
                showAlert(title: "Out of stock", message: "Select a lower quantity.")
            }catch VendingMachineError.insuficientFunds(required: let x){
                showAlert(title: "Insuficient funds", message: "You need to have $\(x) more to make this purchase.")
            }catch let x{
                showAlert(title: "Unknown error", message: "\(x)")
            }

            if let indOfSel = collectionView.indexPathsForSelectedItems?.first{
                collectionView.deselectItem(at: indOfSel, animated: true)
                updateCell(having: indOfSel, selected: false)
            }

        }else{
            showAlert(title: "Invalid selection", message: "Are you sure you selected something?")
        }
    }