openssl ca: make index.txt parsing error more verbose
openssl ca: make index.txt parsing error more verbose

If index.txt exists but has some problems (like for example a single \n character in it) openssl will just exit without any error message.

Bug at least expirienced twice: https://superuser.com/questions/1327848/openssl-ca-fails-after-password-without-error-message

Reviewed-by: Paul Dale <ddec78389666b4f7c9b4d110380c848489a3e4aa@openssl.org>
Reviewed-by: Tomas Mraz <2bc6038c3dfca09b2da23c8b6da8ba884dc2dcc2@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/15360)

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl