AppleScript with list selection and Cancel button suppressed or disabled
I had the same problem today and found this way out:

set theChoice to choose from list


is returning the list's choice or "false" when the user clicks "Cancel"

So I used it for a loop – honestly quite a bit dirty, but it works.

repeat until endloop is true
    set theChoice to choose from list
    if goTo is not false then
        beep
        display alert "Noo!"
    else
        set endloop to true
    end if
end repeat


I hope I was helpful with my first post in here.