Godot “无效的获取索引'转换'（在基础上;无'）。错误

问：

我正在遵循一些教程，typiyng与教程中的人完全相同，但是当我尝试运行项目时，我得到了“无效的获取索引'transform'（在基础上;NIL'） 错误'，我真的不知道为什么

extends CharacterBody3D


const SPEED = 5.0
const JUMP_VELOCITY = 4.5

@export var TILT_LOWER_LIMIT := deg_to_rad(-90.0)
@export var TILT_UPPER_LIMIT := deg_to_rad(90.0)
@export var CAMERA_CONTROLLER : Camera3D

var _mouse_input : bool = false
var _mouse_rotation : Vector3
var _rotation_input : float
var _tilt_input : float

# Get the gravity from the project settings to be synced with RigidBody nodes.
var gravity = ProjectSettings.get_setting("physics/3d/default_gravity")

func _input(event):
    if event.is_action_pressed("exit"):
        get_tree().quit()
        
func _unhandled_input(event):
    _mouse_input = event is InputEventMouseMotion and Input.get_mouse_mode() == Input.MOUSE_MODE_CAPTURED
    if _mouse_input:
        _rotation_input = -event.relative.x
        _tilt_input = -event.relative.y
        print(Vector2(_rotation_input,_tilt_input,))
        
func _update_camera(delta):
    
    # Rotate camera using euler rotation
    _mouse_rotation.x += _tilt_input * delta
    _mouse_rotation.x = clamp(_mouse_rotation.x, TILT_LOWER_LIMIT, TILT_UPPER_LIMIT)
    _mouse_rotation.y += _rotation_input * delta
    
    CAMERA_CONTROLLER.transform.basis = Basis.from_euler(_mouse_rotation)
    CAMERA_CONTROLLER.rotation.z = 0.0
    
    _rotation_input = 0.0
    _tilt_input = 0.0
        
func _ready():
    Input.mouse_mode = Input.MOUSE_MODE_CAPTURED

func _physics_process(delta):
    # Add the gravity.
    if not is_on_floor():
        velocity.y -= gravity * delta
        
    _update_camera(delta)

    # Handle Jump.
    if Input.is_action_just_pressed("jump") and is_on_floor():
        velocity.y = JUMP_VELOCITY

    # Get the input direction and handle the movement/deceleration.
    # As good practice, you should replace UI actions with custom gameplay actions.
    var input_dir = Input.get_vector("move_left", "move_right", "move_forward", "move_backward")
    var direction = (transform.basis * Vector3(input_dir.x, 0, input_dir.y)).normalized()
    if direction:
        velocity.x = direction.x * SPEED
        velocity.z = direction.z * SPEED
    else:
        velocity.x = move_toward(velocity.x, 0, SPEED)
        velocity.z = move_toward(velocity.z, 0, SPEED)

    move_and_slide()

如果需要，这里是脚本和场景树

我第三次检查了我的代码，但看不到任何问题，我确定我犯了一些愚蠢的语法错误，但又看不出在哪里。 此外，如果我删除所有引用CAMERA_CONTROLLER项目的内容，并且CAMERA_CONTROLLER引用 Camera3D，以及其中的某些内容，脚本就看不到，

我尝试重新输入脚本两次，但问题仍然存在，将重置相机 3d 位置更改为 0 并仅使用 CameraController 移动它。