help with shooting projectile along a curve path

hey guys, so i been trying to find a way to shoot projectiles along a curve path . and i found this tutorial on youtube which was really good. here (https://www.youtube.com/watch?v=IvT8hjy6q4o)

i also uploaded the project in case you wanted to check it out. here (http://www.mediafire.com/file/z5zfqbcnpznnbsh/arc+luncher.unitypackage)

but there is problem with this script .if i move the target object somewhere above the starting point the curved path will be disappeared and i get couple of errors.in fact when ever the path is about to become a straight line the errors will pop up . here is the screenshot of errors (https://ibb.co/vZ5JTZ2) and here is a gif file to show when the problem shows up (https://i.stack.imgur.com/ibCD9.gif) and finally here is the code responsible for calculating the curve path a lunching projectiles.

 public Transform startPoint;
     public Transform target;
     public int resolution = 30;
     public float curveHight = 25;
     public float gravity = -18;
 
     
     public Rigidbody bullet;
     public LineRenderer lineRenderer;
     void Start()
     {
 
     }
 
     void Update() {
 
 
 
 
         DrawPath();
 
         
         if (Input.GetKeyDown(KeyCode.Space))
         {
             Launch();
         }
 
        
     }
 
     void Launch()
     {
 
         Rigidbody clone = Instantiate(bullet, startPoint.position, Quaternion.identity);
 
         Physics.gravity = Vector3.up * gravity;
 
         clone.velocity = CalculateLaunchData().initialVelocity;
     }
 
     LaunchData CalculateLaunchData()
     {
         float displacementY = target.position.y - startPoint.position.y;
         Vector3 displacementXZ = new Vector3(target.position.x - startPoint.position.x, 0, target.position.z - startPoint.position.z);
         float time = Mathf.Sqrt(-2 * curveHight / gravity) + Mathf.Sqrt(2 * (displacementY - curveHight) / gravity);
         Vector3 velocityY = Vector3.up * Mathf.Sqrt(-2 * gravity * curveHight);
         Vector3 velocityXZ = displacementXZ / time;
 
         return new LaunchData(velocityXZ + velocityY * -Mathf.Sign(gravity), time);
     }
 
     void DrawPath()
     {
         LaunchData launchData = CalculateLaunchData();
         Vector3 previousDrawPoint = startPoint.position;
 
 
         for (int i = 1; i <= resolution; i++)
         {
             float simulationTime = i / (float)resolution * launchData.timeToTarget;
             Vector3 displacement = launchData.initialVelocity * simulationTime + Vector3.up * gravity * simulationTime * simulationTime / 2f;
             Vector3 drawPoint = startPoint.position + displacement;
             Debug.DrawLine(previousDrawPoint, drawPoint, Color.green);
 
             previousDrawPoint = drawPoint;
 
             lineRenderer.positionCount = resolution;
 
             lineRenderer.SetPosition(i - 1, drawPoint);
         }
     }
 
     struct LaunchData
     {
         public readonly Vector3 initialVelocity;
         public readonly float timeToTarget;
 
         public LaunchData(Vector3 initialVelocity, float timeToTarget)
         {
             this.initialVelocity = initialVelocity;
             this.timeToTarget = timeToTarget;
         }
 
     }
 }

so,any idea what might be causing the the problem?