Fix cast AIOB error

[Novemser]

Original row.set(row.fieldCount(), targetDataType, null); will surely cause AIOB error since row.fieldCount() number is out of bound.

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This change is 

[ilovesoup]

LGTM

[Novemser]

Need add this to integration test case.

Like

select c1,cast(max(c2)as String) c2, max(c4) c4 from tb group by c1 limit 1

Need to add null data row.