Can anyone help me what is wrong with this script?

This is the roll a ball player script. On unity it says as following

‘Assets/senes/Builds_Data/Managed/Assembly-CSharp.dll’ shouldn’t be queried by IsAssemblyCompatible, missing IsInternalOrCompiledAssembly check ?

Does anyone know what this means exactly? If you do pleas tell me what to do.

using UnityEngine;
using System.Collections;
using UnityEngine.UI;

public class PlayerController : MonoBehaviour {

    public float speed;
    public Text countText;
    public Text winText;

    private Rigidbody rb;
    private int count;

    void Start ()
    {
        rb = GetComponent<Rigidbody>();
        count = 0;
        SetCountText();
        winText.text = "";
    }

    void FixedUpdate()
    {
        float moveHorizontal = Input.GetAxis("Horizontal");
        float moveVertical = Input.GetAxis("Vertical");

        Vector3 movement = new Vector3(moveHorizontal, 0.0f, moveVertical);

        rb.AddForce(movement * speed);
    }
    void OnTriggerEnter(Collider other)
    {
        if (other.gameObject.CompareTag("Pick Up"))
        {
            other.gameObject.SetActive(false);
            count = count + 1;
            SetCountText();
        }
    }

    void SetCountText ()
    {
        countText.text = "Count: " + count.ToString();
        if (count >= 11)
        {
            winText.text = "You Win";
        }

    }
}

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