How to make GameObject target = null after raycast hit

Unity Engine
1

I know how to do this with triggers and colliders but I don’t know how to do it with raycasting in place.

This is what I have for my raycast script so far:

using UnityEngine;
using System.Collections;

public class Raycasting : MonoBehaviour {
	
	public bool hasHit = false;
	public GameObject slotObject;
	
	
	// Use this for initialization
	void Start () {
	
	}
	
	// Update is called once per frame
	void Update () {
		
		RaycastHit hit;
		float distcance = 5;
		
		if(Physics.Raycast(transform.position,  transform.TransformDirection(new Vector3(0,5,0)), out hit, distcance))
		{
			if(hit.collider.gameObject.tag == "Slot")
			{
				float distanceToObject = hit.distance;
				slotObject = GameObject.FindGameObjectWithTag("Slot");
				slotObject.renderer.material.color = Color.blue;
				Debug.Log("Distance" + hit.distance);
			}
		}
		Debug.DrawRay (transform.position, transform.TransformDirection(new Vector3(0,5,0)), Color.green);
	}
}

It works ok when hitting an object, I just need to know how to make it know its hitting nothing.

Cheers

2 
if(Physics.Raycast(transform.position,  transform.TransformDirection(new Vector3(0,5,0)), out hit, distcance)) {
	if(hit.collider.gameObject.tag == "Slot") {
		float distanceToObject = hit.distance;
		slotObject = GameObject.FindGameObjectWithTag("Slot");
		slotObject.renderer.material.color = Color.blue;
		Debug.Log("Distance" + hit.distance);
	}
} else {
        // We didn't hit anything
}
3 
if(!Physics.Raycast(transform.position,  transform.TransformDirection(new Vector3(0,5,0)), out hit, distcance)) {
}

add a ! in the if to check it return null mean no collider is being hit
(another way to check)