Yes i know, I checked it but i did not fully understand it, It just shows how to toggle it off i think.
The script linked above (post 2) will work as long as you make the Night-Eye spell an ability. What it's saying is:
If (player) already has Night-Eye active, remove it.
Otherwise, (Night-Eye isn't active), add it.
To implement this, make two spells. One the Night-Eye ability (this is the one you will reference in the script, checking if it's active), and one a regular spell the player can cast (This is the spell you attach the script to). When the player casts the spell (begin script effect), it will toggle the ability on or off.
Hope this helps.