Datatable Sorting

Hi,

I have a datatable consisting of 5 columns where each column may or may not have data.I need to sort the data in the datatable in ascending or descending order which I am able to do but I have a requirement that if a particular column is empty , then the data should not get sorted.
Here is a snippet:
http://webix.com/snippet/eddf07a2.

In this snippet, even though the year column is empty, the data in the other columns are getting sorted which should not happen.In addition, I don’t know which column will have empty data(as the data is coming dynamically;two or more columns may also be empty).

Can you please help me out as how to acheive the above functionality ?
Thanks

You can use the onHeaderClick event to prevent the following sorting for the empty column:

http://webix.com/snippet/ced69af4