[Solved] filterExpr Filtering for Null values client side

[j]

Hi, I have implemented the client side filtering boxes.  I want to filter for blanks or null.  I have added some code the the filtering JS in the view to attempt to set the filter when the user types "null" into the filter box.  What is the filterExpr for finding rows with null in them?

Here is my code: 

  		if (column.type == "String") {
                        if (value == "null") {
                            filterExpr = column.member + " IS Null"
                        } else {
                            filterExpr = column.member + "~substringof~'" + value + "'";
                        }
                    } else {
                        filterExpr = column.member + "~eq~" + value;
                    }