no clear error when channel opening failing when no room in utxos for change

[RodriFS]

Since there is no way to calculate the fees before the PSBT is generated, we can't warn the user that there is no room in utxos for fees when doing operations with change. At least now there is a warning if the amount is equal which might happen if the user forgets to click on changeless. And also added a clear error message (visible to the user) when this happens