BUG #19000: gist index returns inconsistent result with gist_inet_ops

The following bug has been logged on the website:

Bug reference:      19000
Logged by:          Alexander Lakhin
Email address:      exclusion@gmail.com
PostgreSQL version: 18beta2
Operating system:   Ubuntu 24.04
Description:

The following script:
CREATE EXTENSION btree_gist;

CREATE TABLE t AS SELECT '192.168.1.0/25'::inet AS i;

SELECT * FROM t WHERE i << '192.168.1.0/24'::cidr;
       i
----------------
 192.168.1.0/25

CREATE INDEX ON t USING gist(i);

SELECT * FROM t WHERE i << '192.168.1.0/24'::cidr;
 i
---
(0 rows)

shows an inconsistency when using the "<<" operator with a gist index.

Reproduced starting from be1cc9aaf.