script works in Script Editor but not as app (MacOS Mojave)
You need to do two things in order to get this to run:

First of all you need to make sure System Events itself has permissions in the Accessibility preference pane.

Secondly, you should add a delay after clicking the menu item to give it time to load.  That ultimately is what is causing the index error, because the menu hasn't propagated yet and it's trying to access items in it.  Change your script to the following:

....
        click nord
    end ignoring
end tell
delay 0.3
do shell script "killall System\\ Events"
....