rusk-wallet: Default value will not prevent a transaction from being signed

[HDauven]

Describe the bug When doing a transfer/stake with a zero balance, the user should get a "balance too low" warning by default. Instead, now the user can use the default values to sign a transaction, which will obviously fail.

Only when the user fills in a value, will they get a warning by the wallet that they need to fill in a value in the range of 0.000000001-0. When using either 1 LUX or 0, the user is now blocked from continuing, which is not the case if the default value is selected.

To Reproduce

1. Create a new wallet or address with a 0 balance
2. Navigate to transfer or stake
3. Use all default values to create a transaction
4. The wallet will give you an error
5. Now try again, and change the value to transfer, the wallet should block the creation of a transaction with a range based error message blocking input

Expected behaviour If the user has a zero balance, they should not be able to go through the process to begin with. They should be given a warning that their balance is too low to do the requested action.