Handle empty concat nodes in NFA builder; fixes tests we regressed in the protoregexes branch.
Handle empty concat nodes in NFA builder; fixes tests we regressed in the protoregexes branch.

cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp