Unexpected result when using `LEVENSHTEIN`

[suyZhong]

Describe the bug
Consider the following test cases. I suppose the first query is unexpected: it should return only one row, as the UNION ALL of three queries returns only one row 1 false. Besides, if first insert true in table t0 and then false, the first query returns only one row as expected.

To Reproduce

DROP TABLE IF EXISTS t0 CASCADE;
DROP TABLE IF EXISTS t1 CASCADE;

CREATE TABLE t0 (c0 BOOLEAN);
CREATE TABLE t1 (c1 INT) ;
INSERT INTO t1(c1) VALUES (1);

INSERT INTO t0(c0) VALUES (false); -- should first insert false then true
INSERT INTO t0(c0) VALUES (true);

SELECT * FROM t1 LEFT  JOIN t0 ON LEVENSHTEIN(t0.c0, true); -- 1 false, 1, true (unexpected)
SELECT * FROM t1 LEFT  JOIN t0 ON LEVENSHTEIN(t0.c0, true) WHERE t0.c0 UNION ALL SELECT * FROM t1 LEFT  JOIN t0 ON LEVENSHTEIN(t0.c0, true) WHERE (NOT t0.c0) UNION ALL SELECT * FROM t1 LEFT  JOIN t0 ON LEVENSHTEIN(t0.c0, true) WHERE ((t0.c0) IS NULL); -- 1 false

SELECT LEVENSHTEIN(true, true); -- 0
SELECT LEVENSHTEIN(t0.c0, true) FROM t0; -- 4, 4 (I guess it's unexpected and the root cause)

Expected behavior
As mentioned above.

Screenshots
N/A

Software versions
Build from source:

> docker exec -it monetdb-test mserver5 --version
MonetDB 5 server 11.52.0 (hg id: 736987f) (64-bit, 128-bit integers)
This is an unreleased version
Copyright (c) 1993 - July 2008 CWI
Copyright (c) August 2008 - 2023 MonetDB B.V., all rights reserved
Visit https://www.monetdb.org/ for further information
Found 503.5GiB available memory, 128 available cpu cores
Libraries:
Compiled by: @2195e8c5ad70 (x86_64-pc-linux-gnu)
Compilation: /usr/bin/cc 
Linking    : /usr/bin/ld

Issue labeling
Bug

Additional context
Add any other context about the problem here.