Remove object assignment in runtime?

You might want to rephrase that. I am not sure if this answer is anything you were looking for because your question is hard to understand.

You remove a gameobject like this:

GameObject.Destroy(gameObject);

When doing so, any references to that game object or any components that were attached will become nullified, so you need to take this into consideration if other scripts reference the object or any of its children (including scripts etc).

if (thatReference == null)
{
    // The object is gone!
}

Since unity objects implement an implicit boolean cast operator you can shorten that to:

if (!thatReference)
{
    // The object is gone!
}

And similarily you can make null-safe code such as:

if (thatReference)
{
    // OK to use thatReference!
}