get rid of more undefined behaviour in TrackListMerger

[mmusich]

resolves #39229

PR description:

Follow-up to #37384 (comment).

PR validation:

To be tested in this PR, according to #39229 (comment) it passes integration tests.

If this PR is a backport please specify the original PR and why you need to backport that PR. If this PR will be backported please specify to which release cycle the backport is meant for:

N/A

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-39233/31857

• This PR adds an extra 20KB to repository

[cmsbuild]

A new Pull Request was created by @mmusich (Marco Musich) for master.

It involves the following packages:

• RecoTracker/FinalTrackSelectors (reconstruction)

@jpata, @cmsbuild, @mandrenguyen, @clacaputo can you please review it and eventually sign? Thanks.
@VourMa, @felicepantaleo, @GiacomoSguazzoni, @JanFSchulte, @rovere, @VinInn, @gpetruc, @mmusich, @mtosi, @dgulhan 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

[mmusich]

@cmsbuild, please test

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-7493a5/27160/summary.html
COMMIT: 72655bb
CMSSW: CMSSW_12_6_X_2022-08-28-2300/el8_amd64_gcc10
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week0/cms-sw/cmssw/39233/27160/install.sh to create a dev area with all the needed externals and cmssw changes.

Comparison Summary

Summary:

• No significant changes to the logs found
• Reco comparison results: 2 differences found in the comparisons
• DQMHistoTests: Total files compared: 51
• DQMHistoTests: Total histograms compared: 3695708
• DQMHistoTests: Total failures: 16
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 3695670
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 50 files compared)
• Checked 212 log files, 49 edm output root files, 51 DQM output files
• TriggerResults: no differences found

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-39233/31882

• This PR adds an extra 20KB to repository

[cmsbuild]

Pull request #39233 was updated. @jpata, @cmsbuild, @mandrenguyen, @clacaputo can you please check and sign again.

[mmusich]

@cmsbuild, please test

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-7493a5/27185/summary.html
COMMIT: 71dfa03
CMSSW: CMSSW_12_6_X_2022-08-29-2300/el8_amd64_gcc10
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week0/cms-sw/cmssw/39233/27185/install.sh to create a dev area with all the needed externals and cmssw changes.

Comparison Summary

Summary:

• No significant changes to the logs found
• Reco comparison results: 4 differences found in the comparisons
• DQMHistoTests: Total files compared: 51
• DQMHistoTests: Total histograms compared: 3696018
• DQMHistoTests: Total failures: 20
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 3695976
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 50 files compared)
• Checked 212 log files, 49 edm output root files, 51 DQM output files
• TriggerResults: no differences found

[mandrenguyen]

+reconstruction
It would have been preferable had the author agreed to remove the additional line break introduced by this PR, which creates a spurious diff.

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next master IBs (tests are also fine). This pull request will now be reviewed by the release team before it's merged. @perrotta, @dpiparo, @rappoccio (and backports should be raised in the release meeting by the corresponding L2)

[perrotta]

+1