`_path.get_path_collection_extents`, when applied to a collections with `offsets=[]` treats the offsets as if they were [0, 0](this behavior is used in path.get_paths_extents). This interpretation of an empty collection is error-prone, and caused #1490. Hence it would be desirable to decide what should `path.get_path_collection_extents` return when given an empty collection, and have `path.get_path_extents` not rely on current behavior. This issue is created to not lose track of the bug, while closing #1490 and merging #1497.