I think you guys really need to be more relaxed. Call of the void is nothing to worry about or even be scared of. Almost everyone has these kind of thoughts every now and then. Actually, you should be more worried if you never thought of this before. Call of the void, as well as bizarre mind games, strange dreams, etc are necessary "vacations" of your mind from stress and all the many rules how to behave in our everyday life. It restores your mind to normality. Like watching a movie with drama and suspense just for fun.
Enjoy the view from heights, as long as you don't jump, you're perfectly fine.
And instead of spending lots of money on talking to your therapist about it, you rather donate that money to people who suffer from really terrible stuff.