BUG: IS NOT NULL on RECORD variable fails in 17.5-dev

Hello,
I have discovered what appears to be a severe bug in a development version
of PostgreSQL 17 where a populated RECORD variable incorrectly fails an IS
NOT NULL check.

Version Information:

PostgreSQL 17.5 (Debian 17.5-1) on x86_64-pc-linux-gnu, compiled by gcc
(Debian 14.2.0-19) 14.2.0, 64-bit

*Minimal Reproducible Example:*

DO $$
DECLARE
r RECORD;
BEGIN
RAISE NOTICE '--- Assigning a row with a NULL column into "r" ---';
SELECT 42 AS id, NULL::text AS name INTO r;
RAISE NOTICE 'The value of r is: %', r;
ASSERT r IS NOT NULL, 'ASSERTION FAILED: r IS NULL!';
RAISE NOTICE 'Assertion Passed.';
END $$;

*Actual Output:*
NOTICE: --- Assigning a row with a NULL column into "r" ---
NOTICE: The value of r is: (42,)
ERROR: ASSERTION FAILED: r IS NULL!
CONTEXT: PL/pgSQL function inline_code_block line 8 at ASSERT

*Expected Output:* The ASSERT should pass without error. The RAISE NOTICE
proves the record is populated immediately before the ASSERT fails. Thank
you.