Protect against motherless leptons

[mseidel42]

PR description:

Fixes #39250

Note that the crash only occurs for old particle guns before 93b170d (12_3_X)

PR validation:

Ran 9000 events from /eos/cms/store/relval/CMSSW_12_0_1/RelValSingleMuPt10/MINIAODSIM/120X_mcRun3_2021_realistic_v7-v1/10000/03e1cf94-8b28-40ad-8fde-2597e215d1a6.root which crashed before as the single leptons did not have any mothers for older particle gun samples.

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-39270/31918

• This PR adds an extra 12KB to repository

[cmsbuild]

A new Pull Request was created by @mseidel42 (Markus Seidel) for master.

It involves the following packages:

• GeneratorInterface/RivetInterface (generators)

@SiewYan, @mkirsano, @Saptaparna, @cmsbuild, @alberto-sanchez, @menglu21, @GurpreetSinghChahal can you please review it and eventually sign? Thanks.
@alberto-sanchez, @mkirsano this is something you requested to watch as well.
@perrotta, @dpiparo, @rappoccio you are the release manager for this.

cms-bot commands are listed here

[perrotta]

test parameters:

• workflows =10001.0, 10003.0, 10006.0, 10801.0

[perrotta]

type bugfix

[perrotta]

please test

[perrotta]

urgent

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-bf7447/27231/summary.html
COMMIT: fc32d85
CMSSW: CMSSW_12_6_X_2022-08-31-1100/el8_amd64_gcc10
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week0/cms-sw/cmssw/39270/27231/install.sh to create a dev area with all the needed externals and cmssw changes.

Comparison Summary

@slava77 comparisons for the following workflows were not done due to missing matrix map:

• /data/cmsbld/jenkins/workspace/compare-root-files-short-matrix/data/PR-bf7447/10001.0_SingleElectronPt10+2017+SingleElectronPt10_pythia8_GenSim+Digi+RecoFakeHLT+HARVESTFakeHLT+ALCA+Nano
• /data/cmsbld/jenkins/workspace/compare-root-files-short-matrix/data/PR-bf7447/10003.0_SingleElectronPt1000+2017+SingleElectronPt1000_pythia8_GenSim+Digi+RecoFakeHLT+HARVESTFakeHLT+ALCA+Nano
• /data/cmsbld/jenkins/workspace/compare-root-files-short-matrix/data/PR-bf7447/10006.0_SingleMuPt1+2017+SingleMuPt1_pythia8_GenSim+Digi+RecoFakeHLT+HARVESTFakeHLT+ALCA+Nano
• /data/cmsbld/jenkins/workspace/compare-root-files-short-matrix/data/PR-bf7447/10801.0_SingleElectronPt10+2018+SingleElectronPt10_pythia8_GenSim+Digi+RecoFakeHLT+HARVESTFakeHLT+ALCA+Nano

Summary:

• No significant changes to the logs found
• Reco comparison results: 4 differences found in the comparisons
• DQMHistoTests: Total files compared: 55
• DQMHistoTests: Total histograms compared: 4024071
• DQMHistoTests: Total failures: 20
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 4024029
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 54 files compared)
• Checked 236 log files, 49 edm output root files, 55 DQM output files
• TriggerResults: no differences found

[perrotta]

+1

• The fix is quite logic, the previously failing workflows now succeed: let have it merged in order to have a few more workflows fixed in the next IBs
• @cms-sw/generators-l2 please complain if you think there is anything missing or wrong

[perrotta]

merge