Fix Wasabi crash if exception happens after PreviewTx screen

[Szpoti]

Addresses #11191
Addresses #10171
and probably more in the future.

Already suggested this fix in the past for different problems, not sure why it was not accepted.

At this point, if an exception does occur somehow even before trying to finalize and send, just when we build the tx, we should raise the exception and throw out a message because something is deffinetly not ok, and we can prevent the wallet crash as well.

This PR just widens the try/catch.

[adamPetho]

Already suggested this fix in the past for different problems, not sure why it was not accepted.

I think it was not accepted before because this approach is just hides the problem and wraps it inside a try-catch block.
Instead of fixing the real issues that can come up in this part of send workflow.

I think showing an error dialog is a tiny bit better than crashing the software, but still the issue is there just as before, and we don't present a solution to the user how to overcome the issue.

[Szpoti]

but still the issue is there just as before, and we don't present a solution to the user how to overcome the issue.

I absolutely agree with this, the main problem should be found & fixed at the deeper level.
But I still think this way is better as we deflect any crash that can happen. What we can also do to improve, is to create a more detailed try/catch block here, and catch and show various exceptions differently.

[Szpoti]

To note

This PR doesn't fix the main, deep problem of #11191 and #10171, this just fixes the wallet crashing because of these kind of errors.

var transaction = await Task.Run(() => TransactionHelpers.BuildTransaction(_wallet, _info));

TransactionHelpers.BuildTransaction() doesnt have a try/catch inside, because every other call of this function is wraped in a try/catch outside. Everywhere, but here, causing the crash.

[molnard]

tACK