Object reference not set to an instance of an object - Jumping Scripts (C#)

I'm trying to jump and execute in another script when the player collides with an object using this code in a script that checks for a collision named "CheckCollisions":

 using UnityEngine;
 using System.Collections;
 
 public class CheckCollision : MonoBehaviour {
     private GameObject Player;
     private EndlessMode Jumpscripts;
     // Use this for initialization
     void Start () {
         Player = GameObject.Find ("Player");
     }
      void OnCollisionEnter2D(Collision2D Player) {
         Debug.Log ("Collision Detected");
         Jumpscripts.StopGame ();
     }
 }

The script its jumping to ("EndlessMode") has this line of code that it should be executing:

 using UnityEngine;
 using UnityEngine.UI;
 using System.Collections;
 
 public class EndlessMode : MonoBehaviour {
 
         public void StopGame () {
             HasPlayerDied = true;
         }
 }

But when the Player does collide with an obsticle, executing the CheckCollision "OnCollisionEnter2D" function, i get the following error:

"NullReferenceException: Object reference not set to an instance of an object CheckCollision.OnCollisionEnter2D (UnityEngine.Collision2D Player) (at Assets/Scripts/CheckCollision.cs:20)"