Update TriggerDataAccess.py - fix how tapis handles triggers seeded by "L1All", which have no l1item

Fixes https://its.cern.ch/jira/browse/ATR-30370 Tested with:

tapis /eos/atlas/atlasdatadisk/rucio/mc23_13p6TeV/54/47/AOD.41608847._000009.pool.root.1 chains "*L1All"

Before this fix, the assertion error is encountered. After this fix, the list of L1All trigger chains is correctly displayed.