Late initialize editing controls

addons/terrain-editing/terrain_editing_plugin.gd

@@ -3,24 +3,23 @@ extends EditorPlugin
 
 const CONTAINER := CustomControlContainer.CONTAINER_SPATIAL_EDITOR_SIDE_RIGHT
 
-var controls_scene  := preload("res://terrain/editing/TerrainEditingControls.tscn")
-var controls_script := preload("res://terrain/editing/TerrainEditingControls.cs")
-
-var controls : Control;
+var controls: Control = null;
 
 func _handles(object: Object) -> bool:
-	return object.get_script() == controls_script
-
-func _enter_tree() -> void:
-	controls = controls_scene.instantiate()
+	var script := object.get_script() as CSharpScript
+	return script and script.resource_path.ends_with("/Terrain.cs")
 
 func _exit_tree() -> void:
+	if not controls: return
 	if controls.get_parent():
 		remove_control_from_container(CONTAINER, controls)
 	controls.free()
 
 func _make_visible(visible: bool) -> void:
 	if visible:
+		if not controls:
+			var controls_scene = load("res://terrain/editing/TerrainEditingControls.tscn")
+			controls = controls_scene.instantiate()
 		add_control_to_container(CONTAINER, controls)
-	elif controls.get_parent():
+	elif controls and controls.get_parent():
 		remove_control_from_container(CONTAINER, controls)