Get the correct times out of a report if any

The function to retrieve the start and end time out of a FJR had a
bug where a None time would make it return always a None stopTime.

Fix it and also don't allow the ErrorHandler to get stuck if
the jobs don't have running time information.
Merge pull request #4385 from dballesteros7/fixTimesInReport

Get the correct times out of a report if any