I wish to apologize if my previous answer was short or rude, I was a bit rushed. Page 25 of the rules may be the closest thing to what you're wanting. There it says explicitly that zero damage is the same as no damage, i.e. it is not damage. It also says how your total dice roll needs to be higher than zero for you to deal damage. However, I think page 14 may be more important to the discussion where it discusses the difference between life and damage. This is because we need to remember that damage isn't just something that happens in mage wars. It's actually a stat all its own that is tracked separately from life. Taking damage literally means increasing your damage stat in mage wars. If you didn't increase this stat, you didn't take damage. Plain and simple.
