Commit 90eb1a40eb4498b8bcfd73e67cbc69a0eaab1423
2020-09-25T12:36:32
[subset] In ChainContextFormat3 don't skip subsetting if backtrack or lookahead are empty. It's valid to have a ChainContextFormat3 with either an empty backtrack or lookahead. Only drop the lookup if the input sequence is empty.