Grid column combo filter bug

When u have column combo filter and some of the rows in the grid dont have values the combo filter shows an empty select row which is fine BUT when u select the empty row to filter by it and display all the grid rows which have no value for this very column it simply HIDES all the rows.

Expected result: Selecting an empty value from the drop down combo should filter the grid by those rows which have no value for this column.

Actual result: Hides all the rows in the grid and it appears ampty.

P.S.

Is there a way to predefine an empty combo row text. For example instead of empty string - “n/a” or “Rows without values for this column”

when u select the empty row to filter by it and display all the grid rows which have no value for this very column it simply HIDES all the rows.

For me, when you select an “empty option” of the combo filter it unfilters the grid, which is a default behavior of all grid in-header filters.

Is there a way to predefine an empty combo row text. For example instead of empty string - “n/a” or “Rows without values for this column”

There is no possibility to customize the combo filter options list.
In your case, I can suggest you to use an external filter with the required logic:
https://docs.dhtmlx.com/suite/grid/usage/#filtering-data