This version of Unity is unsupported.
Removed

Component.collider

Obsolete Property collider has been deprecated. Use GetComponent<Collider>() instead. public Component collider;

Description

The Collider attached to this GameObject. (Null if there is none attached).

using UnityEngine;

public class Example : MonoBehaviour { void Start() { GetComponent<Collider>().material.dynamicFriction = 1; } }