NullReferenceException: Object reference not set to an instance of an object - I understand the issue but can't find the solution

Finally fixed a bunch of errors and pulled through only to find I got this basic ass problem that is stopping me from playtesting my scripts. I know this is a super common issue with new users, and that's exactly what I am, only my second game in the making so help is much appreciated.
The problem is in my Move method, it says I haven't set an instance of an object but I'm unsure on how to do so in this particular situation. All I'm trying to do is get my ball to finally get somewhere damn it! Thanks in advance!

Here's the code:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class PlayerController : MonoBehaviour
 {
     public float moveSpeed;
     public float drag = 0.5f;
     public float terminalRotationSpeed = 25.0f;
     public Vector3 MoveVector { set; get; }
 
     private Rigidbody rb;
     private Transform cam_transform;
 
     void Start()
     {
         rb = gameObject.AddComponent<Rigidbody>();
         rb.maxAngularVelocity = terminalRotationSpeed;
         rb.drag = drag;
     }
 
     void Update()
     {
         MoveVector = PoolInput();
 
         MoveVector = RotateWithView();
 
         Move();
     }
 
     private void Move()
     {
         rb.AddForce(MoveVector * moveSpeed);
     }
 
     private Vector3 PoolInput()
     {
         Vector3 dir = Vector3.zero;
 
         dir.x = Input.GetAxis("Horizontal");
         dir.z = Input.GetAxis("Vertical");
 
         if (dir.magnitude > 1)
             dir.Normalize();
         return dir;
     }
 
     private Vector3 RotateWithView()
     {
         if(cam_transform != null)
         {
             Vector3 dir = cam_transform.TransformDirection(MoveVector);
             dir.Set(dir.x, 0, dir.z);
             return dir.normalized * MoveVector.magnitude;
         }
         else
         {
             cam_transform = GetComponent<ThirdPersonCamera>().camTransform;
         }
         return new Vector3();
     }
 }