No EventToken returned when CollectionTree exists but has 0 events
In the case of skimmed samples the CollectionTree is created even if no event passes the selection eventually (as opposed to xAODs produced in Athena). Now, when trying to read such a file we currently throw an error as the file is readable but no event token can be obtained, even though it should.
Likely culprit: TQSample.cxx:194