Unexpected error `baseBuiltinFunc.vecEvalInt() should never be called, please contact the TiDB team for help`

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)

The following test case triggered an unexpected error `baseBuiltinFunc.vecEvalInt() should never be called, please contact the TiDB team for help`

```
CREATE TABLE t0(c0 BOOL);
INSERT IGNORE INTO t0 VALUES (false);
SET @b = NULL;
SET @c = NULL;
PREPARE prepare_query FROM 'SELECT ((NULLIF(?, ?))OR(t0.c0)) FROM t0';
EXECUTE prepare_query USING @b,@c;
```

### 2. What did you expect to see? (Required)

No error.

### 3. What did you see instead (Required)

`baseBuiltinFunc.vecEvalInt() should never be called, please contact the TiDB team for help`

### 4. What is your TiDB version? (Required)

Release Version: v9.0.0-beta.2.pre-196-g312226f869\nEdition: Community\nGit Commit Hash: 312226f869d56922135e1c177cac6c90319c3134\nGit Branch: HEAD\nUTC Build Time: 2025-09-21 08:27:14\nGoVersion: go1.23.11\nRace Enabled: false\nCheck Table Before Drop: false\nStore: unistore\nKernel Type: Classic