Without this, the 'Apply Filter' button only becomes active after the user manually changes the selection in the drop down. Since there is no longer a place holder, the 'Apply Filter' button should be active when the control renders since the first item is selected. I am not sure why the `set` call you highlighted above is not triggering this but I found(just tested to confirm) that I needed this handler in order for the 'Apply Filter' button to be activated.