Yakut Mon fails to gracefully handle empty bitmask and sparse_list

When a node publishes a empty bitmask or sparse list for the on the uavcan.node.port.List publishers and subscrivbers topic, Yakut fails to handle it correctly.

  uavcan_node_port_SubjectIDList_1_0_select_mask_(&port_list.publishers);

  uavcan_node_port_SubjectIDList_1_0_select_sparse_list_(&port_list.subscribers);

  size_t size = uavcan_node_port_List_1_0_SERIALIZATION_BUFFER_SIZE_BYTES_;
  uint8_t buf[size];

  uavcan_node_port_List_1_0_serialize_(port_list, buf, &size);

OS: Ubuntu 24.04
Yakut Version: git release 3a22dd4
Installation method: pip3

Error:

pycyphal.util._broadcast: Unhandled exception in <bound method Avatar._on_trace of Avatar(node_id=42)>: 
Traceback (most recent call last):
  File "/home/opencyphal/.venv/lib/python3.12/site-packages/pycyphal/util/_broadcast.py", line 46, in delegate
    r: typing.Union[R, Exception] = fn(*args, **kwargs)
                                    ^^^^^^^^^^^^^^^^^^^
  File "/home/opencyphal/.venv/lib/python3.12/site-packages/yakut/cmd/monitor/_model.py", line 165, in _on_trace
    handler(float(ts.monotonic), obj)
  File "/home/opencyphal/.venv/lib/python3.12/site-packages/yakut/cmd/monitor/_model.py", line 102, in _on_port_list
    self._ports.pub = expand_subjects(obj.publishers)
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/opencyphal/.venv/lib/python3.12/site-packages/yakut/cmd/monitor/_model.py", line 198, in expand_subjects
    assert False
           ^^^^^
AssertionError

Start in yakut/cmd/monitor/_model.py, following _on_port_list into expand_subjects, where the traceback shows the assertion. Reproduce the monitor input with empty publishers or subscribers bitmasks and sparse lists, then verify that both forms are handled without an AssertionError.