Addressbook script: managing missing values

I am writing a script to export my addressbook contacts to a csv file. Depending on the contact, some of the data may be missing. I am then getting certain fields such as organization, in the csv file that appear as “missing value”.

How can I detect that an address book field is empty or not?

Something like this might work:

tell application "Address Book"
	set person_ to properties of person 1
	if organization of person_ is missing value then
		set mv to true
		-- deal with missing value
	else
		set mv to false
		-- the value exists - include it in the export
	end if
end tell

if mv is true then display dialog "no org"

– Rob