I was able to enter and approve an wrap order at 0 USDC on xUSD.
Similarly, it was possible to enter an unwrap order from 0 xUSD to USDC.
I think STX Bridge should check if the entered USDC /xUSD value is greater than 0.
If it is equal or less than 0, the associated notification should appear and/or the (Un)Wrap key should not be active (not selectable).
Google Chrome 106.0.5249.119 (ver)