HLT DQM: add protection for empty L1 uGT collection

[fwyzard]

No description provided.

[fwyzard]

8.1.x version of #14474

[fwyzard]

please test

[cmsbuild]

The tests are being triggered in jenkins.
https://cmssdt.cern.ch/jenkins/job/ib-any-integration/12948/console

[cmsbuild]

A new Pull Request was created by @fwyzard (Andrea Bocci) for CMSSW_8_1_X.

It involves the following packages:

DQM/HLTEvF

@cmsbuild, @dmitrijus, @vanbesien, @deguio, @davidlange6 can you please review it and eventually sign? Thanks.
@slava77, @Degano, @smuzaffar you are the release manager for this.

cms-bot commands are list here #13028

[dmitrijus]

+1

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_8_1_X IBs after it passes the integration tests. This pull request requires discussion in the ORP meeting before it's merged. @slava77, @davidlange6, @Degano, @smuzaffar

[davidlange6]

+1

[cmsbuild]

+1
Tested at: 9558fcf
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-14475/12948/summary.html

The following merge commits were also included on top of IB + this PR after doing git cms-merge-topic:
08a43c3
60b365b
d89f2c1
b7e7db3
5e93ffa
You can see more details here:
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-14475/12948/git-log-recent-commits
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-14475/12948/git-merge-result

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-14475/12948/summary.html