Collection download crashes if hda has no extension

[galaxyproject-sentryintegration]

This happens if tools don't define an output format. It's a tool bug, but I think falling back to data as a default extension is reasonable.

Sentry Issue: GALAXY-MAIN-YRR

ExceptionGroup: unhandled errors in a TaskGroup
  File "starlette/_utils.py", line 87, in collapse_excgroups
    yield
  File "starlette/middleware/base.py", line 190, in __call__
    async with anyio.create_task_group() as task_group:
  File "anyio/_backends/_asyncio.py", line 678, in __aexit__
    raise BaseExceptionGroup(

AttributeError: 'NoneType' object has no attribute 'endswith'
(29 additional frame(s) were not displayed)
...
  File "galaxy/webapps/galaxy/services/history_contents.py", line 482, in get_dataset_collection_archive_for_download
    return self.__stream_dataset_collection(trans, dataset_collection_instance)
  File "galaxy/webapps/galaxy/services/history_contents.py", line 501, in __stream_dataset_collection
    archive = hdcas.stream_dataset_collection(
  File "galaxy/managers/hdcas.py", line 39, in stream_dataset_collection
    write_dataset_collection(dataset_collection_instance, archive)
  File "galaxy/managers/hdcas.py", line 50, in write_dataset_collection
    for file_path, relpath in hda.datatype.to_archive(dataset=hda, name=name):
  File "galaxy/datatypes/data.py", line 451, in to_archive
    if dataset.datatype.composite_type or dataset.extension.endswith("html"):