block: fix miner assertion failure.
block: fix miner assertion failure.

decentraland/bronzeage-node,decentraland/bronzeage-node,decentraland/decentraland-node,VidaID/bcoin,decentraland/decentraland-node,decentraland/decentraland-node,decentraland/bronzeage-node,VidaID/bcoin,VidaID/bcoin