`array_element`, `array_any_value` use list offsets to deduce nullability.

[tabac]

Describe the bug

The array_element, array_any_value UDFs use a ListArray's offsets to deduce that a row is Null. If the difference between two consecutive offsets is 0 then the row should be Null.

This goes against the Arrow spec which allows positive slot lengths for Null rows.

It should be noted that a null value may have a positive slot length. That is, a null value may occupy a non-empty memory space in the data buffer. When this is true, the content of the corresponding memory space is undefined.

Expected behavior

The ListArray's null buffer should be used instead.