Avoid including runs without an end from long ago

[cfuselli]

If a run ends badly without an end time in the run database, we do not want to include it in the runs selection.
Here I added a logic that adds that when looking for runs without an end (so, also the current running runs) we make sure that the start time of such run is within the last six hours.

This should fix the problems observed in the plots with runs too old being included.

[mflierm]

Great, thaaanks a lot! Maybe 3-4 hours would already be sufficient since we rarely take longer runs anyway, but this is a good start so let's see how it goes!