kdc: Don’t use uninitialized variable

The call to free_KDCDHKeyInfo(), further down, could have caused heap
corruption.

Found by Coverity (Samba CID 1544611).

Signed-off-by: Joseph Sutton <josephsutton@catalyst.net.nz>

kdc/pkinit.c

@@ -1045,9 +1045,9 @@ pk_mk_pa_reply_dh(krb5_context context,
         unsigned char *p;
         ret = _kdc_serialize_ecdh_key(context, cp->u.ecdh.key, &p,
                                       &dh_info.subjectPublicKey.length);
-        dh_info.subjectPublicKey.data = p;
         if (ret)
             goto out;
+        dh_info.subjectPublicKey.data = p;
     } else
 	krb5_abortx(context, "no keyex selected ?");