Some ParticleID objects are not always filled

[tmadlener]

For example the RefinedVertex PID object is only conditionally filled. From having had a quick look at the code this seems to mainly be done for some internal caching(?).

I am mainly opening this issue since I have stumbled over this while updating the LCIO <-> EDM4hep conversion for accommodating key4hep/EDM4hep#268 . I am not sure if there is an easy fix, but I would at least like to have some paper trail to document the reason for some implementations that might need to work around this fact.

[Zehvogel]

This is also an issue for the jet clustering. In particular when there is an event where no jet is found no PID object is created.

[tmadlener]

Closing this since iLCSoft/LCIO#193 and iLCSoft/MarlinReco#135 make it possible to let the user decide whether they want all of the collections have this or none of them.