jqxGrid: cutom filter widget as drop down

[SvetoslavjQWidgets]

Describe the bug There is a situation where the grid's filter row is a custom widget and is a drop-down with checkboxes. When you search for an item in the drop-down and try to select the first one, it cannot be selected

To Reproduce Steps to reproduce the behaviour:

1. Go to https://jsfiddle.net/v31kphub/1/
2. Click on 'Select filter' of the first column
3. Type 'c' in the search field
4. See that the first checkbox cannot be deselected
5. Remove 'c'
6. Deselect everything
7. Type 'c' again
8. See that the checkbox cannot be selected