Sending tx with default "0 amount" not handling correctly

[KarboDuck]

1. Open classic Karbo Wallet v 1.4.9.
2. On send tab fill in address and press send.

Result:
Wallet shows "Sending transactions" status but doesn't do anything probably because by default amount was set to 0.

It is almost non-issue, because wallet can be used further normally and after editing amount send will work correctly.

Expected:
Warning about no amount specified. Or better just highlight "Amount" field with red color blink.

Also look at issue43. Check should execute before asking for password and payment id, not after.

[aivve]

Should be fixed in f8fbed7 and db7424c