[monero-project/monero] tx_pool: fix infinite loop when failing to find a meta record (#4276)

vtnerd commented on this pull request.

> @@ -1146,6 +1146,7 @@ namespace cryptonote
if (!m_blockchain.get_txpool_tx_meta(sorted_it->second, meta))
{
MERROR(» failed to find tx meta»);
+ sorted_it++;

Should this be a `for` loop instead? It looks like the only branch that doesn’t `++` is the `break` which exits.