Make sure lumiTree is written to empty NTuple files
Since empty NTuple files are created by RootHistSvc, we try to find the file that service created and use it.
@efranzos, @erodrigu, @egraveri, with this change we can add back the lumiTree check to the test DaVinciTests.davinci.test_davinci_tupling_with_lumi_from_spruce_noEventsInSelection
Useful to be tested with DaVinci!990 (merged) to avoid 2 cycles of CI tests.
Edited by Eduardo Rodrigues