player name tags not always facing camera of every client (PhotonNetwork)

hey guys i tried to get this working but no luck i am using photon network and i wanted all my other players name tags to face me in my client and with the other players the other way arround so my UIText will face them in their client i did post a simular post befour but didnt think it was clear what i wanted i have this script on the canvas that is above the characters /players is thare a way of doing this ?.. also i put in the if statement so when thare are no players accept me it wil not bug and if i have only my client no bug but as soon as i startup an other client it say refference not set to an instance of an object becouse it can`t find a main camera here is the script

 public class BilBord_Face_Camera : MonoBehaviour
 {
     private Transform mainCameraTransform;
 
     private void Start()
     {
         mainCameraTransform = Camera.main.transform;
     }
 
     private void LateUpdate()
     {
         if(mainCameraTransform == null)
         {
 
         }
         else
         {
             transform.LookAt(transform.position + mainCameraTransform.rotation * Vector3.forward,
             mainCameraTransform.rotation * Vector3.up);
         }
 
     }
     
 }