Assertion failed: Assertion failed on expression: 'pos < this->m_num_bits'

using UnityEngine;
using System.Collections;

// Performs a mouse look.

public class FPSInput : MonoBehaviour
{
    public float speed;
    private CharacterController My_controller;

    private void Start()
    {
        My_controller = GetComponent<CharacterController>();
    }

    private void Update()
    {
        PlayerMove();
    }

    private void PlayerMove()
    {
        bool gravity_vector = false;
        move_vector = Vector3.zero;
        if (Input.GetKey(KeyCode.W))
        {
            transform.position += transform.forward * speed * Time.deltaTime;
        }
    }

}