Wallet transaction database corruption possible

[braydonf]

If there is an unexpected event, a crash, shutdown, power-loss or similar when a block is being added to the wallet, it can possibly lead to invalid state for the wallet with some transactions left unconfirmed or missing entirely.

The tip for the wallet is set before the transactions have been completely added. Thus if there is an issue, and the transactions are not added. The next startup will begin at the next block, instead adding the block again and adding all of the transactions.

The relevant lines of code are in addBlock of lib/wallet/walletdb.js:
https://github.com/bcoin-org/bcoin/blob/master/lib/wallet/walletdb.js#L1978-L1991

Those missing or unconfirmed transactions can then lead to cascading issues with other transactions failing to confirm from an assertion, assert(coin.height !== -1), in confirm() of lib/wallet/txdb.js: https://github.com/bcoin-org/bcoin/blob/master/lib/wallet/txdb.js#L663