Fall threw floor when I unchrouch unity3d

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class crouch : MonoBehaviour
{
CharacterController controller;
// Start is called before the first frame update
void Start()
{

}
// Update is called once per frame
void FixedUpdate()
{
if (Input.GetKey(KeyCode.LeftControl) ) {
controller = GetComponent();
controller.height = 1.0f;
}
else
{
controller = GetComponent();
controller.height = 3.8f;

}
}
}
here is script

How to report problems correctly in the Unity3D forums:

http://plbm.com/?p=220