DSA: Make DSA_bits() and DSA_size() check that there are key parameters

DSA: Make DSA_bits() and DSA_size() check that there are key parameters

Without these check, a DSA structure without key parameters will cause
these functions to crash.  This is also the case in pre-3.0 OpenSSL,
but since we now extract these data early, to cache them in the
EVP_PKEY structure, the same crash happens earlier and much more
internally.

The added checks are of the same kind as DSA_security_bits() already
does.

Fixes #13610

Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
(Merged from https://github.com/openssl/openssl/pull/13611)