Do we need a wrapper function here? I am guessing bch-js had some reason to include this. But it seems kind of strange. Ideally the function would just return "true" or "false" --- instead of this wrapper version that returns strings, which then need to be parsed by the app.

It's okay for this diff since we are matching legacy functionality, but we should add another part to this stack to clean it up.

Rabbit hole to library function points here: https://github.com/bitcoinjs/bip39/blob/master/src/index.js#L66

Maybe a blank string does return a false positive. But in this case, we should just also control for blank strings, not persist an artifact wrapper function of questionable value in Cashtab.