Fixes for when listtransactions encounters non-standard outputs

Bugfix: Avoid trying to parse outputs that aren't relevant to CWalletTx::GetAmounts
* This fixes a warning when an output we aren't concerned with can't be parsed.

Bugfix: Supress "address" key in transaction details, when the destination isn't recognized
* Previously, it would pass corrupt/random through base58.

Fixes #779 and #1848.