TypeError: data type 'u0' not understood

[tlambert03]

just got this by running an MDA without having loaded a system config. In should fail more gracefully:

File ~/dev/self/napari-micromanager/.venv/lib/python3.12/site-packages/superqt/utils/_ensure_thread.py:179, in _run_in_thread(func=<function _NapariMDAHandler._on_mda_started>, thread=<PyQt6.QtCore.QThread object>, await_return=False, timeout=1000, args=(<napari_micromanager._mda_handler._NapariMDAHandler object>, MDASequence(metadata={'pymmcore_widgets': {'vers...False, interval=datetime.timedelta(0), loops=10))), kwargs={})
    177 future = Future()  # type: ignore
    178 if thread is QThread.currentThread():
--> 179     result = func(*args, **kwargs)
        func = <function _NapariMDAHandler._on_mda_started at 0x1400980e0>
        args = (<napari_micromanager._mda_handler._NapariMDAHandler object at 0x151cb8e90>, MDASequence(metadata={'pymmcore_widgets': {'version': '0.7.2'}, 'napari_micromanager': {'split_channels': False}}, axis_order=('t', 'p', 'c'), stage_positions=(Position(x=None, y=None, z=None, name=None, sequence=None),), channels=(Channel(config='', group='Channel', exposure=100.0, do_stack=True, z_offset=0.0, acquire_every=1, camera=None),), time_plan=TIntervalLoops(prioritize_duration=False, interval=datetime.timedelta(0), loops=10)))
        kwargs = {}
    180     if not await_return:
    181         future.set_result(result)

File ~/dev/self/napari-micromanager/src/napari_micromanager/_mda_handler.py:103, in _NapariMDAHandler._on_mda_started(self=<napari_micromanager._mda_handler._NapariMDAHandler object>, sequence=MDASequence(metadata={'pymmcore_widgets': {'vers...False, interval=datetime.timedelta(0), loops=10)))
    101 dtype = f"u{self._mmc.getBytesPerPixel()}"
    102 # create the zarr array and add it to the viewer
--> 103 z = zarr.open(
        tmp = <TemporaryDirectory '/var/folders/30/fpzwkh4103s6xj67y2k0q4pr0000gn/T/tmpl4t9gdfy'>
        str(tmp.name) = '/var/folders/30/fpzwkh4103s6xj67y2k0q4pr0000gn/T/tmpl4t9gdfy'
        tmp.name = '/var/folders/30/fpzwkh4103s6xj67y2k0q4pr0000gn/T/tmpl4t9gdfy'
        yx_shape = [0, 0]
        shape = [10, 1, 1]
        shape + yx_shape = [10, 1, 1, 0, 0]
        dtype = 'u0'
        tuple([1] * len(shape) + yx_shape) = (1, 1, 1, 0, 0)
        [1] * len(shape) + yx_shape = [1, 1, 1, 0, 0]
        [1] * len(shape) = [1, 1, 1]
        len(shape) = 3
    104     str(tmp.name),
    105     shape=shape + yx_shape,
    106     dtype=dtype,
    107     chunks=tuple([1] * len(shape) + yx_shape),  # VERY IMPORTANT FOR SPEED!
    108 )
    109 # get filename from MDASequence metadata
    110 fname = _get_file_name_from_metadata(sequence)

File ~/dev/self/napari-micromanager/.venv/lib/python3.12/site-packages/zarr/convenience.py:127, in open(store='/var/folders/30/fpzwkh4103s6xj67y2k0q4pr0000gn/T/tmpl4t9gdfy', mode='a', zarr_version=None, path='', **kwargs={'chunks': (1, 1, 1, 0, 0), 'dtype': 'u0', 'path': '', 'shape': [10, 1, 1, 0, 0]})
    125 elif mode == "a":
    126     if "shape" in kwargs or contains_array(_store, path):
--> 127         return open_array(_store, mode=mode, **kwargs)
        _store = <zarr.storage.DirectoryStore object at 0x308069370>
        kwargs = {'shape': [10, 1, 1, 0, 0], 'dtype': 'u0', 'chunks': (1, 1, 1, 0, 0), 'path': ''}
        mode = 'a'
    128     else:
    129         return open_group(_store, mode=mode, **kwargs)

File ~/dev/self/napari-micromanager/.venv/lib/python3.12/site-packages/zarr/creation.py:618, in open_array(store=<zarr.storage.DirectoryStore object>, mode='a', shape=[10, 1, 1, 0, 0], chunks=(1, 1, 1, 0, 0), dtype='u0', compressor='default', fill_value=0, order='C', synchronizer=None, filters=None, cache_metadata=True, cache_attrs=True, path='', object_codec=None, chunk_store=None, storage_options=None, partial_decompress=False, write_empty_chunks=True, zarr_version=2, dimension_separator=None, meta_array=None, **kwargs={})
    616 # ensure fill_value of correct type
    617 if fill_value is not None:
--> 618     fill_value = np.array(fill_value, dtype=dtype)[()]
        fill_value = 0
        np = <module 'numpy' from '/Users/talley/dev/self/napari-micromanager/.venv/lib/python3.12/site-packages/numpy/__init__.py'>
        dtype = 'u0'
    620 # ensure store is initialized
    622 if mode in ["r", "r+"]:

TypeError: data type 'u0' not understood