Otherwise reading some of the records like ESM::CellRef without a subrecord
after could lead to underflow of ESM_Context::leftRec which makes
ESM::ESMReader::hasMoreSubs to return true and load hangs for a while trying to
read the same subrecord many times.
Fix ESM::Variant tests since it's now required to have a record for any ESM
data. Add 16 (size of record header) to all expected data sizes.
2e64155c0f