Add default operations to EC_METHOD

Reviewed-by: Rich Salz <rsalz@openssl.org>

crypto/ec/ec_key.c

diff --git a/crypto/ec/ec_key.c b/crypto/ec/ec_key.c
index 2ff4449..3b02eca 100644
--- a/crypto/ec/ec_key.c
+++ b/crypto/ec/ec_key.c
@@ -234,11 +234,7 @@
 
 int ossl_ec_key_gen(EC_KEY *eckey)
 {
-    if (eckey->group->meth->keygen == NULL) {
-        ECerr(EC_F_OSSL_EC_KEY_GEN, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
-        return 0;
-    }
-
+    OPENSSL_assert(eckey->group->meth->keygen != NULL);
     return eckey->group->meth->keygen(eckey);
 }