Does it cost in performance if I have mesh colliders without a mesh attached?

I have a method of importing meshes with separate collision meshes. In my import settings I click generate colliders. Before I make them a prefab I drag them in the viewport then I delete the collision meshes from the objects that are not named collision something. But I don't delete the mesh collider component because it says that I will lose my connection with the original model. Does unity discard these null mesh collider when playing or it costs something?

Am I doing it all wrong ?

In short I use one invisible mesh collider for all the objects and I delete from all the rest of the objects the mesh attached to the mesh collider component (but not the mesh collider component itself). I do that so I can keep ovewriting files from 3ds apps and update automatically my prefabs.

When it says the thing about losing the connection, just do it. It doesn't hurt anything and is not an error. Having a component does cost something; not sure how much in this case, but there if there's no point having it, then get rid of it.