'buffer' must be non-NULL as isc_buffer_allocate can no longer fail.

1636 cleanup:

CID 1458130 (#1 of 1): Dereference before null check (REVERSE_INULL)
check_after_deref: Null-checking buffer suggests that it may be
null, but it has already been dereferenced on all paths leading to
the check.

1637        if (buffer != NULL)
1638                isc_buffer_free(&buffer);

lib/dns/catz.c

@@ -1655,9 +1655,7 @@ dns_catz_generate_zonecfg(dns_catz_zone_t *zone, dns_catz_entry_t *entry,
 	return (ISC_R_SUCCESS);
 
 cleanup:
-	if (buffer != NULL) {
 	isc_buffer_free(&buffer);
-	}
 	return (result);
 }