Fix validation bug and improve color contrast

- Fixed validation error by checking TYPE_DICTIONARY instead of is_empty()
- Removed hardcoded colors, using Godot's built-in theme colors instead

addons/transition_configurator/config_dialog.gd

@@ -77,7 +77,6 @@ func _ready() -> void:
 	
 	room_filter_label = Label.new()
 	room_filter_label.text = "Showing all rooms"
-	room_filter_label.add_theme_color_override("font_color", Color(0.7, 0.7, 0.7))
 	left_vbox.add_child(room_filter_label)
 	
 	room_list = ItemList.new()
@@ -105,7 +104,6 @@ func _ready() -> void:
 	# Status label
 	status_label = Label.new()
 	status_label.text = ""
-	status_label.add_theme_color_override("font_color", Color(1, 0.5, 0.2))
 	content_vbox.add_child(status_label)
 	
 	# Buttons
@@ -208,7 +206,7 @@ func _validate_selection() -> void:
 		return
 	
 	var arrival_data = arrival_list.get_item_metadata(arrival_idx[0])
-	if arrival_data == null or arrival_data.is_empty():
+	if arrival_data == null or typeof(arrival_data) != TYPE_DICTIONARY:
 		apply_button.disabled = true
 		status_label.text = "Invalid arrival point selected"
 		return
@@ -266,7 +264,11 @@ func _update_bidirectional_connection(dest_scene_path: String, arrival_node_name
 	Update the destination scene to create/update the return transition.
 	Returns empty string on success, error message on failure.
 	"""
-	var current_scene_path = transition_piece.get_tree().edited_scene_root.scene_file_path
+	var current_scene = EditorInterface.get_edited_scene_root()
+	if current_scene == null:
+		return "Could not determine current scene"
+	
+	var current_scene_path = current_scene.scene_file_path
 	var current_room_name = transition_piece.name
 	
 	# Load destination packed scene