[VL] `array_size(null)` results inconsistent with vanilla spark

### Backend

VL (Velox)

### Bug description

`array_size(null)` results inconsistent with vanilla spark.

test sql:

```
SELECT array_size(null)
```

native engine returns: `-1`
vanilla spark returns: `null`



### Spark version

None

### Spark configurations

_No response_

### System information

_No response_

### Relevant logs

_No response_