[ADAM-1099] Make reference region not throw NPE.

[fnothaft]

Resolves #1099.

[AmplabJenkins]

Test FAILed.
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Build result: FAILURE

GitHub pull request #1115 of commit 7dd3022 automatically merged.Notifying endpoint 'HTTP:https://webhooks.gitter.im/e/ac8bb6e9f53357bc8aa8'[EnvInject] - Loading node environment variables.Building remotely on amp-jenkins-worker-05 (centos spark-test) in workspace /home/jenkins/workspace/ADAM-prb > /home/jenkins/git2/bin/git rev-parse --is-inside-work-tree # timeout=10Fetching changes from the remote Git repository > /home/jenkins/git2/bin/git config remote.origin.url https://github.com/bigdatagenomics/adam.git # timeout=10Fetching upstream changes from https://github.com/bigdatagenomics/adam.git > /home/jenkins/git2/bin/git --version # timeout=10 > /home/jenkins/git2/bin/git -c core.askpass=true fetch --tags --progress https://github.com/bigdatagenomics/adam.git +refs/pull/:refs/remotes/origin/pr/ # timeout=15 > /home/jenkins/git2/bin/git rev-parse origin/pr/1115/merge^{commit} # timeout=10 > /home/jenkins/git2/bin/git branch -a --contains b8db4a8f7c5f130ec789458db1554bcb941a288d # timeout=10 > /home/jenkins/git2/bin/git rev-parse remotes/origin/pr/1115/merge^{commit} # timeout=10Checking out Revision b8db4a8f7c5f130ec789458db1554bcb941a288d (origin/pr/1115/merge) > /home/jenkins/git2/bin/git config core.sparsecheckout # timeout=10 > /home/jenkins/git2/bin/git checkout -f b8db4a8f7c5f130ec789458db1554bcb941a288dFirst time build. Skipping changelog.Triggering ADAM-prb ? 2.6.0,2.10,1.5.2,centosTriggering ADAM-prb ? 2.6.0,2.11,1.5.2,centosTouchstone configurations resulted in FAILURE, so aborting...Notifying endpoint 'HTTP:https://webhooks.gitter.im/e/ac8bb6e9f53357bc8aa8'
Test FAILed.

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Test PASSed.
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Test PASSed.

[heuermh]

LGTM

[fnothaft]

This is a trivial change; can I get this merged?

[heuermh]

Merged as commit ca05a86

Thank you, @fnothaft!