Function is_string_null_at 

pub fn is_string_null_at(array: &ArrayRef, i: usize) -> bool

Check whether the string value at index i is null for string or dictionary-encoded string arrays.

Returns true when the value is null or the array type is not a string type, which corresponds to string_array_value_at_index returning None.

Panics

If index i is out of bounds.