Make edm4eic_merge to work for more than tracks

### Environment: (where does this bug occur, have you tried other environments)
main - eic container

### Steps to reproduce: (give a step by step account of how to trigger the bug)
run edm4eic_merge on epic output files.

### Expected Result: (what do you expect when you execute the steps above)
Merged output file

### Actual Result: (what do you get when you execute the steps above)
Segfault when any branches other than SimTrackerHitCollection are included