Embedded node: Possible unhandled promise rejection during sync

[myxmaster]

Describe your enhancement idea

During sync of embedded node, an unhandled promise rejection occurs when the wallet's proof-of-validity (PoV) fails to sync ("unable to sync PoV of the wallet with current best block in the main chain: target hash not found in index", Source: BatchedBridge/NativeModules.js).

Not sure when/why exactly this can happen, probably some neutrino issue, but anyway, we need to improve error handling here.

It would also be nice to implement an auto-recovery mechanism when stuff like this happens (delete neutrino files and restart).