Documentation for the AStar2D, AStar3D, and AStarGrid2D classes' `get_point_path` and `get_id_path` methods doesn't indicate what the return value is if no path is found and `allow_partial_path` is `false`.

**Your Godot version:**
N/A
**Issue description:**
The documentation for the `AStar2D`, `AStar3D`, and `AStarGrid2D` classes' `get_id_path` and `get_point_path` methods doesn't indicate what the return value is (empty array or null?) if no path is found and `allow_partial_path` is `false` (its default value).
**URL to the documentation page (if already existing):**
https://docs.godotengine.org/en/stable/classes/class_astar2d.html#class-astar2d-method-get-id-path
https://docs.godotengine.org/en/stable/classes/class_astar2d.html#class-astar2d-method-get-point-path
https://docs.godotengine.org/en/stable/classes/class_astar3d.html#class-astar3d-method-get-id-path
https://docs.godotengine.org/en/stable/classes/class_astar3d.html#class-astar3d-method-get-point-path
https://docs.godotengine.org/en/stable/classes/class_astargrid2d.html#class-astargrid2d-method-get-id-path
https://docs.godotengine.org/en/stable/classes/class_astargrid2d.html#class-astargrid2d-method-get-point-path