No import of 'id's if event list is empty

[willend]

Working with @damianmr76 on a TBL model, we initially had a mis-positioned Event monitor that as a consequence did not catch any neutrons.

The initial symptom seen was that

with mcstastox.Read(file_path) as loaded_data:
    print(loaded_data.get_components_with_ids())

returned nothing - which we found confusing since the 'pixel-ids' are (geometrically) present irrespective of event data or not.

We suggest to

• List any id'-monitors always
• Add a remark of (Empty) or (No Data) if no events are on the list

[willend]

As side-remark:

Together with Johannes from SCIPP we found a nice way to visualise also 'empty' bins on monitors/detectors. -I suggest to add this in the 'boilerplate' notebook in parallel with the event visualisation:

import scipp as sc
import plopp as pp
da = scipp_object["events"].group(sc.arange('pixel_id', 0, 250000))
da.coords['position'] = scipp_object["positions"]
pp.scatter3d(da.hist(), pos='position', size=0.0015, cbar=True, norm="linear")

(in the event-visualisation, non-illuminated pixels will be translucent / not visible

)