Revert "Don't crash on a missing Subject in index.txt"

This reverts commit 1e05c6d07ff963107286d028f6778d2ccc863a9a.

Empty subjects should be permissible.

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5444)
1 file changed