apps: remove NULL check imn release_engine since ENGINE_free also does it.
apps: remove NULL check imn release_engine since ENGINE_free also does it.

Reviewed-by: Tim Hudson <eb0be8e447f673b41b10eda09d63cd72526b0a42@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/12309)

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