Prevent possible segm violation in TopSingleLeptonHLTOfflineDQM

Prevent possible segm violation in DQMOffline.Trigger.TopSingleLeptonHLTOfflineDQM

The code is quite convoluted, and certainlly something better can be done. 
However, by just allowing for jets the same kind of check on the vector boundary as it is done a few lines above for electrons and muons one can prevent a segmentation violation when the jet selector remove all jets from the vector correctedJets