Fix matching against a NPCG-matching-nothing backref with minCount of 0
Fix matching against a NPCG-matching-nothing backref with minCount of 0

For example, if \1 is a NPCG, \1? is supposed to yield a zero-width match, but instead was treated as a non-match.

Davidebyzero/RegexMathEngine,Davidebyzero/RegexMathEngine