[BUG] NULLIF() function result is wrong

**Describe the bug**

case1: doris own value is different
```
     SELECT NULLIF (91, CAST(69 AS DECIMAL) );
     Result: 0

     SELECT NULLIF (91, CAST(69 AS INT) );
     Results: 91
```

case2: different from mysql value
```
     SELECT ALL NULLIF (-98, NULL) AS col0
     Doris result: NULL
     Mysql result: -98
```

Found through the sqllogictest test case.