CASE WHEN <numeric aggregate> IS NULL THEN null ELSE <numeric aggregate> END` fails with a boolean type error

[YGY-001]

Docker image `apache/age:release_PG18_1.8.0

Reproduction

LOAD 'age';
SET search_path = ag_catalog, public;
SELECT ag_catalog.create_graph('age_issue_case1');

SELECT *
FROM ag_catalog.cypher('age_issue_case1', $$
UNWIND ['GU'] AS alias0
WITH max(toFloat(1)) AS alias2, avg(toFloat(1)) AS alias3
WITH CASE WHEN alias2 IS NULL THEN null ELSE alias2 END AS alias2,
     CASE WHEN alias3 IS NULL THEN null ELSE alias3 END AS alias3
RETURN {alias2: alias2, alias3: alias3} AS result
$$) AS (result agtype);

Expected

One row containing the two numeric aggregate values.

Actual

CASE/ELSE could not convert type double precision to boolean

[gregfelice]

Confirmed still reproducing on current master (4d9b2506, AGE 1.8.0) built against PostgreSQL 18.4, in a fresh database:

ERROR:  CASE/ELSE could not convert type double precision to boolean
LINE 6:      CASE WHEN alias3 IS NULL THEN null ELSE alias3 END AS a...

Triaged as part of a sweep over the current fuzz-report backlog against master. This one is a clean error rather than a crash — recording it so it is not assumed stale just because it was filed against an older image.