Using -i and -C causes segmentation fault

[ehwilliamson]

If CREATE is suppressed, field names are never created: https://github.com/kstrauser/pgdbf/blob/4e847759b5eee96da9dc3d2604e0b555ddd57ccb/src/pgdbf.c#L476-L477

Those field names are used in the ignore code: https://github.com/kstrauser/pgdbf/blob/4e847759b5eee96da9dc3d2604e0b555ddd57ccb/src/pgdbf.c#L538

Using -i with -C (or -u) cause a segfault when strcmp tries to read a nonexistent fieldname.