block: sed-opal: unify error handling of responses

response_get_{string,u64} include error handling for argument resp being
NULL but response_get_token does not handle this.

Make all three of response_get_{string,u64,token} handle NULL resp in
the same way.

Co-authored-by: Jonas Rabenstein <[email protected]>
Signed-off-by: David Kozub <[email protected]>
Signed-off-by: Jonas Rabenstein <[email protected]>
Reviewed-by: Scott Bauer <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: Jon Derrick <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

block/sed-opal.c

@@ -696,6 +696,11 @@ static const struct opal_resp_tok *response_get_token(
 {
 	const struct opal_resp_tok *tok;
 
+	if (!resp) {
+		pr_debug("Response is NULL\n");
+		return ERR_PTR(-EINVAL);
+	}
+
 	if (n >= resp->num) {
 		pr_debug("Token number doesn't exist: %d, resp: %d\n",
 			 n, resp->num);