Fix potential nullptr crashes in TriggerChamberClusterOnTrackCreator

Hi,

this MR fixes potential crashes by checking for nullptrs in TriggerChamberClusterOnTrackCreator.

Best, Nico

This merge request affects 1 package:

• MuonSpectrometer/MuonReconstruction/MuonRIO_OnTrackCreators/MuonCompetingClustersOnTrackCreator

Adding @goetz ,@rosati ,@nkoehler ,@wleight as watchers

added MuonSpectrometer master review-pending-level-1 labels

CI Result SUCCESS (hash 7b78186c)

	Athena	AthSimulation	AnalysisBase	AthGeneration
externals
cmake
make
required tests
optional tests

Full details available on this CI monitor view
Athena: number of compilation errors 0, warnings 0
AthSimulation: number of compilation errors 0, warnings 0
AnalysisBase: number of compilation errors 0, warnings 0
AthGeneration: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 15984]

Hi, looks good thus approving. L1

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

merged

mentioned in commit 99888875

added sweep:ignore label