Unity crashes on GameObject = hit.collider.gameObject;

Hi everyone.

I'm trying to store a raycast-hitted game object in a variable, so I can change the material of it later on. At the moment, Unity crashes every time it runs this particular line of code, the line that says:

 selectedUnit = hit.collider.gameObject;

Here is the code:

 public class SelectUnit : MonoBehaviour {
 
 private Ray ray;
 private RaycastHit hit;
 public GameObject selectedUnit;
 
 void Update () {
     int i = 0;
     while (i < Input.touchCount) {
         if (Input.GetTouch(i).phase == TouchPhase.Began) {
             ray = Camera.main.ScreenPointToRay(Input.GetTouch(i).position);
             if (Physics.Raycast(ray, out hit, 100)) {
                 selectedUnit = hit.collider.gameObject;
                 Debug.Log ("selected unit is: " + selectedUnit.name);
             }
             ++i;
         }
     }
 }
 }

If i omit that line of code with //, the project runs fine, but if it's run, then Unity will crash. Can anybody work out why it crashes?