Mempool's removeBlock doesn't add TXs back if mempool is empty

[mafintosh]

This line seems like a faulty copy/paste:

bcoin/lib/mempool/mempool.js

Lines 246 to 250 in 4c49b08

	async _removeBlock(block, txs) {
	if (this.map.size === 0) {
	this.tip = block.prevBlock;
	return;
	}

[pinheadmz]

Ok I understand this now - it's not a mistake. This guard and the checks in mempool._handleReorg() are in place to make TXs from disconnected blocks reentering the mempool much simpler. The rules for BIP68 (CSV) gets really complicated when TXs re-enter the mempool and I think bcoin handles this in a compatible (if not incomplete) way compared to Bitcoin Core. This is going to a be a bigger issue for Handshake, and I'll open a new issue there.