LArG4HEC: Fix conversion of null pointers to references.

Fix potential conversion of null pointers to references. Fixes ubsan warnings from the ISF_FastCaloSimServices tests.

This merge request affects 1 package:

• LArCalorimeter/LArG4/LArG4HEC

This merge request affects 1 file:

• LArCalorimeter/LArG4/LArG4HEC/src/HECGeometry.cc

Adding @pavol as watcher

added LAr Simulation main review-pending-level-1 labels

CI Result SUCCESS (hash 92f38cf3)

	Athena	AthSimulation
externals
cmake
make
tests

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Athena: number of compilation errors 0, warnings 0
AthSimulation: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-EL9 7291] (remote access info)

added review-approved label and removed review-pending-level-1 label

merged

mentioned in commit 6089e83e