help I keep getting this error on my script?

I keep getting this error on my script ive tried everything–

UnassignedReferenceException: The variable sightLine of ff has not been assigned. You probably need to assign the sightLine variable of the ff script in the inspector. UnityEngine.LineRenderer.SetColors (Color start, Color end) (at C:/buildslave/unity/build/artifacts/generated/common/runtime/GraphicsBindings.gen.cs:1365) ff.simulatePath () (at Assets/darts/ff.cs:89) ff.FixedUpdate () (at Assets/darts/ff.cs:26)

using UnityEngine;
 
 /// <summary>
 /// Controls the Laser Sight for the player's aim
5. /// </summary>
 public class ff : MonoBehaviour
 {
     // Reference to the LineRenderer we will use to display the simulated path
     public LineRenderer sightLine;
10. 
     // Reference to a Component that holds information about fire strength, location of cannon, etc.
     public PlayerFire playerFire;
 
     // Number of segments to calculate - more gives a smoother line
15.     public int segmentCount = 20;
 
     // Length scale for each segment
     public float segmentScale = 1;
 
20.     // gameobject we're actually pointing at (may be useful for highlighting a target, etc.)
     private Collider _hitObject;
     public Collider hitObject { get { return _hitObject; } }
 
     void FixedUpdate()
25.     {
         simulatePath();
     }
 
     /// <summary>
30.     /// Simulate the path of a launched ball.
     /// Slight errors are inherent in the numerical method used.
     /// </summary>
     void simulatePath()
     {
35.         Vector3[] segments = new Vector3[segmentCount];
 
         // The first line point is wherever the player's cannon, etc is
         segments[0] = playerFire.transform.position;
 
40.         // The initial velocity
         Vector3 segVelocity = playerFire.transform.up * playerFire.fireStrength * Time.deltaTime;
 
         // reset our hit object
         _hitObject = null;
45. 
         for (int i = 1; i < segmentCount; i++)
         {
             // Time it takes to traverse one segment of length segScale (careful if velocity is zero)
             float segTime = (segVelocity.sqrMagnitude != 0) ? segmentScale / segVelocity.magnitude : 0;
50. 
             // Add velocity from gravity for this segment's timestep
             segVelocity = segVelocity + Physics.gravity * segTime;
 
             // Check to see if we're going to hit a physics object
55.             RaycastHit hit;
             if (Physics.Raycast(segments[i - 1], segVelocity, out hit, segmentScale))
             {
                 // remember who we hit
                 _hitObject = hit.collider;
60. 
                 // set next position to the position where we hit the physics object
                 segments _= segments[i - 1] + segVelocity.normalized * hit.distance;_

// correct ending velocity, since we didn’t actually travel an entire segment
segVelocity = segVelocity - Physics.gravity * (segmentScale - hit.distance) / segVelocity.magnitude;
65. // flip the velocity to simulate a bounce
segVelocity = Vector3.Reflect(segVelocity, hit.normal);

/*
* Here you could check if the object hit by the Raycast had some property - was
70. * sticky, would cause the ball to explode, or was another ball in the air for
* instance. You could then end the simulation by setting all further points to
* this last point and then breaking this for loop.
*/
}
75. // If our raycast hit no objects, then set the next position to the last one plus v*t
else
{
segments = segments[i - 1] + segVelocity * segTime;
}
80. }

// At the end, apply our simulations to the LineRenderer

// Set the colour of our path to the colour of the next ball
85. Color startColor = playerFire.nextColor;
Color endColor = startColor;
startColor.a = 1;
endColor.a = 0;
sightLine.SetColors(startColor, endColor);
90.
sightLine.SetVertexCount(segmentCount);
for (int i = 0; i < segmentCount; i++)
sightLine.SetPosition(i, segments*);*
}
95. }

The error message is pretty clear.

It not only tells you what’s wrong, but also what to do about it:

The variable sightLine of ff has not
been assigned. You probably need to
assign the sightLine variable of the
ff script in the inspector.