UBSAN issue in TrackListMerger

[smuzaffar]

As a follow up on #37384 , the suggested change #37384 (comment) [a] by @mmusich works for me. Workflow 2323.4.0 did not fail [b] and ubsan issue about RecoTracker/FinalTrackSelectors/plugins/TrackListMerger.cc:451:45: runtime error: variable length array bound evaluates to non-positive value 0 is also fixed. May be we can also move https://github.com/cms-sw/cmssw/blob/master/RecoTracker/FinalTrackSelectors/plugins/TrackListMerger.cc#L364 after the check [a]

@cms-sw/reconstruction-l2 what do you suggest?

[a]

+  if (ngood == 0) {
+    // output empty collections and early return
+    this->returnEmptyCollections(e);
+    return;
+  }

[b]

23234.0_TTbar_14TeV+2026D49+TTbar_14TeV_TuneCP5_GenSimHLBeamSpot14INPUT+DigiTrigger+RecoGlobal+HARVESTGlobal Step0-PASSED Step1-PASSED Step2-PASSED Step3-PASSED  - time date Mon Aug 29 12:01:40 2022-date Mon Aug 29 11:32:36 2022; exit: 0 0 0 0
1 1 1 1 tests passed, 0 0 0 0 failed

[smuzaffar]

assign reconstruction

[cmsbuild]

A new Issue was created by @smuzaffar Malik Shahzad Muzaffar.

@Dr15Jones, @perrotta, @dpiparo, @rappoccio, @makortel, @smuzaffar can you please review it and eventually sign/assign? Thanks.

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[cmsbuild]

New categories assigned: reconstruction

@jpata,@clacaputo,@mandrenguyen you have been requested to review this Pull request/Issue and eventually sign? Thanks

[mmusich]

I've created #39233 with my original suggestion (not yet tested in the last IB), to start the discussion.