Inconsistent result for WEEK()

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)

CREATE TABLE t58 ( c2 int);
INSERT t58 () VALUES (2);
SELECT * FROM t58 WHERE ((WEEK((LOG(4, 2)), 2) - 1));
-- empty set
SELECT * FROM t58 WHERE ((WEEK((LOG(4, c2)), 2) - 1));
-- 2
### 2. What did you expect to see? (Required)
Both queries should return an empty set.
### 3. What did you see instead (Required)
mysql> SELECT * FROM t58 WHERE ((WEEK((LOG(4, c2)), 2) - 1));
+------+
| c2 |
+------+
| 2 |
+------+
1 row in set (0.00 sec)
### 4. What is your TiDB version? (Required)

Release Version: v8.5.0-20251010-ec6b882
Edition: Community
Git Commit Hash: https://github.com/pingcap/tidb/commit/ec6b882d188f77c199907ba26843a872b8c5fd6d
Git Branch: heads/refs/tags/v8.5.0-20251010-ec6b882
UTC Build Time: 2025-10-10 10:21:51
GoVersion: go1.23.3
Race Enabled: false
Check Table Before Drop: false
Store: unistore