Character won't move (Fixed)

I was making a game, and I encountered this problem. The character wouldn't move. This code used to always work but this time, it gives me this error message:

NullReferenceException: Object reference not set to an instance of an object PlayerOneScript1.Movement (Single moveHorizontal) (at Assets/Scripts/PlayerOneScript1.cs:159) PlayerOneScript1.FixedUpdate () (at Assets/Scripts/PlayerOneScript1.cs:155)

Here is the code I wrote:

     public void FixedUpdate()
     {
         float moveHorizontal = Input.GetAxis("Horizontal");
         Movement(moveHorizontal);
     }
     private void Movement(float moveHorizontal)
     {
         rB.velocity = new Vector2(moveHorizontal * playerSpeed, rB.velocity.y);
     }

The first line of code is the 152th line. The character won't move or jump or anything! Help!