Fix crash in ExternalLHEProducer in case of earler exception

[Dr15Jones]

If ExternalLHEProducer throws an exception in begin run, the code will
no longer crash when the module is called in end run.

[cmsbuild]

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

It involves the following packages:

GeneratorInterface/LHEInterface

@efeyazgan, @perrozzi, @thuer, @cmsbuild, @davidlange6, @govoni can you please review it and eventually sign? Thanks.
@alberto-sanchez, @agrohsje, @mkirsano this is something you requested to watch as well.
@davidlange6 you are the release manager for this.

cms-bot commands are listed here

[Dr15Jones]

please test

[cmsbuild]

The tests are being triggered in jenkins.
https://cmssdt.cern.ch/jenkins/job/ib-any-integration/21141/console Started: 2017/07/04 17:24

[Dr15Jones]

This should avoid the seg-faults seen in the IB RelVals for the cases where the external scripts fail to run. (The jobs will still fail, but now they should fail gracefully.)

[cmsbuild]

+1
Tested at: 10267be
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-19549/21141/summary.html

The following merge commits were also included on top of IB + this PR after doing git cms-merge-topic:
2af1298
7775804
f47d787
2b42465
2639355
db12bb5
88e61f1
a405400
e4d2a49
bfe6843
89319f9
d3b3564
e2d2d83
d5de801
4cac99e
236f7c2
b0da358
34923e5
514d35a
aee2fec
526d318
ccc6917
b1580cd
You can see more details here:
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-19549/21141/git-log-recent-commits
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-19549/21141/git-merge-result

[cmsbuild]

Comparison job queued.

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-19549/21141/summary.html

Comparison Summary:

• You potentially added 560 lines to the logs
• Reco comparison results: 1773 differences found in the comparisons
• DQMHistoTests: Total files compared: 22
• DQMHistoTests: Total histograms compared: 1755676
• DQMHistoTests: Total failures: 31740
• DQMHistoTests: Total nulls: 1065
• DQMHistoTests: Total successes: 1722705
• DQMHistoTests: Total skipped: 166
• DQMHistoTests: Total Missing objects: 0
• Checked 90 log files, 14 edm output root files, 22 DQM output files

[perrozzi]

+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 requires discussion in the ORP meeting before it's merged. @davidlange6, @smuzaffar

[davidlange6]

+1