According to the documentation, setting onSort to null on a DataColumn disables sorting for this column.
The implementation has a bug there:
onSort is passed with onSort: () => column.onSort(...) to the _buildHeadingCell method. Within _buildHeadingCell it is checked for null but it never can be.
So clicking a headinig cell leads to a "The method 'call' was called on null." error.

Am I missing something or is this a bug?