Fix input checks wrt legacy code

In all legacy code ctx->cipher is dereferenced without checks, so it
makes no sense to jump there is ctx->cipher is NULL as it will just lead
to a crash. Catch it separately and return an error.

This is simlar to the fix in d2c2e49e

Signed-off-by: Simo Sorce <simo@redhat.com>

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/9002)