Hi,
for Run 3, it is not clear yet, whether we will have CSCs on one side of ATLAS or not. However, to perform layout tests for both cases we need to cover both the case that no CSC chamber will be present and that some CSC chambers will be present. I added UseCSC property to MuonDetectorTool and DetDescrCnvSvc to allow to turn off the hardcoded creation of the CSCIdHelper tool in case we are running without any CSC chamber. Unless the user sets a property from outside, no change compared to the previous implementation is present.