Terrain Disappears on Mouseclicks :(

Hi,

i am able to make up-to below code where i am trying to get co-ordinates(X,Y) on the terrain on mouse-click, apparently i succeeded.

i am able to print coordinates but upon mouse-click

Terrain disappears suddenly and model falls from where it is.

Attaching screen shot for your reference. Please suggest where i am doing wrong, Here comes my complete script.

 using UnityEngine;
 using System.Collections;
 using UnityEditor;
 
 public class TerrainEdit : MonoBehaviour
 {
     // Use this for initialization
     public void Start () 
     {
 
     }
     
     // Update is called once per frame
     void Update () 
     {
         if(Input.GetMouseButtonDown(0))
         {
             RaycastHit hit;
             Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
             if(Physics.Raycast(ray, out hit))
             {
                 transform.position = hit.point;
                 print("First Click: " + transform.position.x + "  ,  " + transform.position.y);
             }
         }
         if(Input.GetMouseButtonDown(1))
         {
             RaycastHit hit;
             Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
             if(Physics.Raycast(ray, out hit))
             {
                 transform.position = hit.point;
                 print("Second Click: " + transform.position.x + "  ,  " +  transform.position.y);
             }
         }
     
     }
 }