Protect against null VertexRef in deep_helpers.cc

[mandrenguyen]

Avoids an invalid reference exception discussed here:
#45190
using the solution suggested by @VinInn

deprecates #45245

Will be backported to 14_0_X

[cmsbuild]

cms-bot internal usage

[cmsbuild]

-code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-45296/40701

• This PR adds an extra 20KB to repository

Code check has found code style and quality issues which could be resolved by applying following patch(s)

• code-format:
  https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-45296/40701/code-format.patch
  e.g. curl -k https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-45296/40701/code-format.patch | patch -p1
  You can also run scram build code-format to apply code format directly

[mandrenguyen]

type btv

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-45296/40702

• This PR adds an extra 20KB to repository

[cmsbuild]

A new Pull Request was created by @mandrenguyen for master.

It involves the following packages:

• RecoBTag/FeatureTools (reconstruction)

@cmsbuild, @jfernan2, @mandrenguyen can you please review it and eventually sign? Thanks.
@Senphy, @demuller, @hqucms, @castaned, @AlexDeMoor, @Ming-Yan, @andrzejnovak, @missirol this is something you requested to watch as well.
@antoniovilela, @rappoccio, @sextonkennedy you are the release manager for this.

cms-bot commands are listed here

[mandrenguyen]

please test

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-a180e7/40055/summary.html
COMMIT: 6eec30b
CMSSW: CMSSW_14_1_X_2024-06-24-2300/el8_amd64_gcc12
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week1/cms-sw/cmssw/45296/40055/install.sh to create a dev area with all the needed externals and cmssw changes.

Comparison Summary

Summary:

• You potentially added 1 lines to the logs
• Reco comparison results: 9 differences found in the comparisons
• DQMHistoTests: Total files compared: 48
• DQMHistoTests: Total histograms compared: 3345088
• DQMHistoTests: Total failures: 6
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 3345062
• DQMHistoTests: Total skipped: 20
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 47 files compared)
• Checked 202 log files, 165 edm output root files, 48 DQM output files
• TriggerResults: no differences found

[mandrenguyen]

+1

[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. @rappoccio, @antoniovilela, @sextonkennedy (and backports should be raised in the release meeting by the corresponding L2)

[rappoccio]

+1