Changing value Custom Attribute Editor value in contributor mode is not enabling "Save" option

We have written a custom attribute editor with two select boxes and saving the two values in a single field. From the UI part of its working fine. But the problem we are facing is when we change a value of these custom attribute for an asset in contributor mode the "Save" option is not getting enabled as expected. To save the values of this custom attribute editor we have to edit some other attribute value of asset and then save the asset to save changed attribute values. I have pasting the JSP code of the element below