I enjoyed the course but I did spend 1.5 days trying to troubleshoot what I was doing differently (I refactor code as I wr...

The simplest way to deal with the 'ZeroDivisionError' in the script would probably be to change

obj.location = sum / n

to

if n > 0:
    obj.location = sum / n

Not necessarily the cleanest way, but it works.

Another way to ensure that the delay doesnt get below 1 :

if not empty.get('_RNA_UI'):
   empty['_RNA_UI'] = {}

empty['delay'] = 10

empty['_RNA_UI']['delay'] = {
"default": 10,
"min":1,
"max":1000}

Found on https://blender.stackexchange.com/questions/143975/how-to-edit-a-custom-property-in-a-python-script

But it's always good practice to ensure Exceptions like zero division error won't be thrown inside the code since the property can be modified by the user