Prevent arithmetic overflow when amount in TransferArgs is below 10_000

[seb-icp]

Currently when requesting a transfer with an amount in TransferArgs below 10_000 e8s the invoice canister will trap on an arithmetic overflow, due to this line :

amount = {
                // Total amount, minus the fee
                e8s = Nat64.sub(Nat64.fromNat(args.amount), 10000);
              };

Is it expected behaviour? I would rather have a specific error indicating that the amount is too low to pay for the fee. For the context, I have a function (called periodically) that check the balance in the invoice canister and request a transfer to another wallet.

[Trunkzz]

I've had this issue a ton. I worked around it by adding 10,000 extra.

[krpeacock]

Some better error handling here would be worthwhile