message: fix fork_database::prune (was not erasing all invalid forks)
diff: @@ -201,8 +201,7 @@ namespace eosio { namespace chain {
  my->index.erase(itr);
  auto& numidx = my->index.get<by_block_num>();
  - auto nitr = numidx.find( num );
  - if( nitr != numidx.end() ) {
  + for( auto nitr = numidx.lower_bound( num ); nitr != numidx.end() && (*nitr)->block_num == num; ++nitr ) {
  remove( (*nitr)->id );
  }
  }
  