Throw exception if TFile::Open returns nullptr

[Dr15Jones]

PR description:

The InputFile does not function properly if TFile::Open returns nullptr.

PR validation:

A case where TFile::Open returned nullptr was seen in CMSSW_10_6 in case where we tested reading a file generated in CMSSW_13_3 in that older release.

[Dr15Jones]

please test

[Dr15Jones]

@smuzaffar the bot didn't seem to notice this PR.

[Dr15Jones]

@makortel FYI

[cmsbuild]

cms-bot internal usage

[smuzaffar]

@smuzaffar the bot didn't seem to notice this PR.

@Dr15Jones , thanks for reporting. While fixing the issue mentioned #43706 (comment) (bot restting the signatures for squashed PRs) I introduce a bug and that is why bot was not reacting to new PR. This is fixed now

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-43920/38772

• This PR adds an extra 12KB to repository

[cmsbuild]

A new Pull Request was created by @Dr15Jones (Chris Jones) for master.

It involves the following packages:

• IOPool/Input (core)

@Dr15Jones, @smuzaffar, @makortel can you please review it and eventually sign? Thanks.
@wddgit, @makortel this is something you requested to watch as well.
@sextonkennedy, @rappoccio, @antoniovilela you are the release manager for this.

cms-bot commands are listed here

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-1e651e/37310/summary.html
COMMIT: cf7fa70
CMSSW: CMSSW_14_1_X_2024-02-08-1100/el8_amd64_gcc12
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week1/cms-sw/cmssw/43920/37310/install.sh to create a dev area with all the needed externals and cmssw changes.

Comparison Summary

Summary:

• You potentially added 98 lines to the logs
• Reco comparison results: 53 differences found in the comparisons
• DQMHistoTests: Total files compared: 48
• DQMHistoTests: Total histograms compared: 3248626
• DQMHistoTests: Total failures: 1186
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 3247418
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 47 files compared)
• Checked 200 log files, 161 edm output root files, 48 DQM output files
• TriggerResults: no differences found

[makortel]

The usual

• spurious differences in outputs of Run-3 wfs *.7 #39803
• Non reproducibility in wf 136.793 #43293
• Non-reproducibility in TriggerResults in 24834.0, 24834.911, and 25034.999 #43790

[makortel]

+core

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

[rappoccio]

+1