Am I using isNull() correctly in this function for a custom module called Listings?  I can't get it to work.  The only argument is listing_id.  The function is supposed to execute when a Listing is created or updated.

// listing fields

listing_record = zoho.crm.getRecordById("Listings",listing_id);

listing_street_name = listing_record.get("Street_Name");

listing_street_number = listing_record.get("Street_Number");

listing_temp_street_address = listing_record.get("Temp_Street_Address");

listing_street_direction = listing_record.get("Dir");

listing_street_type = listing_record.get("Street_Type");

listing_mls_number = listing_record.get("MLS_Number");

listing_list_date = listing_record.get("List_Date");

// function

listing_map = Map();

if(listing_street_number.isNull())

{

street_address = listing_temp_street_address.proper();

}

else

{

street_address = listing_street_number + if(listing_street_direction.isNull(),""," " + listing_street_direction) + if(listing_street_name.isNull(),""," " + listing_street_name.proper()) + if(listing_street_type.isNull(),""," " + listing_street_type.proper());

}

// name listing

listing_name = street_address + " - " + if(listing_mls_number.isNull(),if(listing_list_date.isNull(),""," " + listing_list_date)," " + listing_mls_number);

listing_map.put("Name",listing_name);

listing_map.put("Temp_Street_Address",street_address);

listing_map.put("Street_Name",street_address);

// update listing

update_response = zoho.crm.updateRecord("Listings",listing_id.toLong(),listing_map);

info listing_map;

info update_response;