Don't leak memory on error in PKCS12_key_gen_uni

The PKCS12_key_gen_uni() had one error path which did not free memory
correctly.
Reviewed-by: NRichard Levitte <levitte@openssl.org>

crypto/pkcs12/p12_key.c

@@ -129,7 +129,7 @@ int PKCS12_key_gen_uni(unsigned char *pass, int passlen, unsigned char *salt,
     v = EVP_MD_block_size(md_type);
     u = EVP_MD_size(md_type);
     if (u < 0)
-        return 0;
+        goto err;
     D = OPENSSL_malloc(v);
     Ai = OPENSSL_malloc(u);
     B = OPENSSL_malloc(v + 1);