How to deal damage at mob only and not at items

Hi, I'm working on a mod where the sword allows you to send a lightning strike on entities within 20 blocks around the player by right-clicking. The problem is that it also affects items on the ground and armor stands. I’ve attached a picture of my procedure.

I hope someone can help me because it's really unfortunate as a problem, and a simple misclick could be problematic if a valuable item gets destroyed.

(Translated from French to English by ChatGPT)