case 'I': { if (TESTAFF(rv->astr, 'J', rv->alen)) numsyllable += 1; break; }
probably ought to be
case 'I': { if (rv && TESTAFF(rv->astr, 'J', rv->alen)) numsyllable += 1; break; }
The same snippet appears twice in the file, but the null check was forgotten in one case (the wonders of code duplication ;)
Fixed in the CVS. Thanks, László