Protect CSCOfflineMonitor from crashing when job ends early

If the cmsRun job ended before the beginRun was called, CSCOfflineMonitor would seg fault. We now protected against that condtion.
Merge pull request #1876 from Dr15Jones/avoidCrashInCSCOfflineMonitorWhenJobEndsEarly

DQM fixes -- Protect CSCOfflineMonitor from crashing when job ends early