You will only ever have one bullet at the path "/root/Main/Bullet". This bullet is named "Bullet".
Other bullets that are added to your scene will be called "Bullet2" and "Bullet3". Godot auto-numbers them. They will not be recognized by your code, since your code only looks for "Bullet".
So, if you ever have more than one bullet, your code isn't going to work properly.
For example, if you have two bullets on screen named "Bullet" and "Bullet2", and Bullet is freed before Bullet2 enters the enemy, then you are going to get an error since your code is looking for Bullet, which no longer exists.
Try this instead:
if "Bullet" in body.name: