GeneratorObjectsTPCnv: Fix use of invalidated iterators.

Reverts previous incorrect change. Fixes test failures in the hepmc2 build.

This merge request affects 1 package:

• Generators/GeneratorObjectsTPCnv

This merge request affects 1 file:

• Generators/GeneratorObjectsTPCnv/src/initMcEventCollection.cxx

Adding @gemmeren as watcher

added Generators main review-pending-level-1 labels

CI Result SUCCESS (hash 0943a0c3)

	Athena	AthSimulation	AthGeneration	AthAnalysis
externals
cmake
make
tests

Full details available on this CI monitor view. Check the JIRA CI status board for known problems
Athena: number of compilation errors 0, warnings 0
AthSimulation: number of compilation errors 0, warnings 0
AthGeneration: number of compilation errors 0, warnings 0
AthAnalysis: number of compilation errors 0, warnings 0
For experts only: Jenkins output (remote access info)

Passing to L2 to crosscheck because I'm not really sure what's happening here

Kira (L1)

added review-pending-level-2 label and removed review-pending-level-1 label

Looks good. Karolos (L2)

added review-approved label and removed review-pending-level-2 label

merged

mentioned in commit 01c862f0