Protect InDetPhysVal against crash due to missing HS vertex

Add protection against non-identified reconstructed HS vertex to avoid crashes in samples with low track multiplicity HS vertex (H4nu,Hgamgam, etc.)

This merge request affects 1 package:

• InnerDetector/InDetValidation/InDetPhysValMonitoring

This merge request affects 1 file:

• InnerDetector/InDetValidation/InDetPhysValMonitoring/src/InDetPerfPlot_VertexTruthMatching.cxx

Adding @goetz ,@sroe as watchers

added InnerDetector master review-pending-level-1 labels

CI Result SUCCESS (hash dca0db49)

	Athena	AthSimulation	AthGeneration	AnalysisBase
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
AthGeneration: number of compilation errors 0, warnings 0
AnalysisBase: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 25140]

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

merged

mentioned in commit cc9b22f3

added sweep:ignore label