Explicit handling of no-spikes during curation

[CBroz1]

The extraction notebooks use try/except to skip instances of no units found.

The notebook:

spyglass/notebooks/py_scripts/40_Extracting_Clusterless_Waveform_Features.py

Lines 176 to 180 in 448fffd

	for sorting_id in sorting_ids:
	try:
	sgs.CurationV1.insert_curation(sorting_id=sorting_id)
	except KeyError as e:
	pass

This KeyError is potentially thrown by the process that looks for spike times in the units object:

spyglass/src/spyglass/spikesorting/v1/curation.py

Lines 351 to 354 in 448fffd

	units_dict = {
	unit_id: spike_times
	for unit_id, spike_times in zip(units.index, units["spike_times"])
	}

Instead of using a KeyError to handle this case, we should either handle the null entry (i.e., #849) or raise a more specific error