Fix for the masked module hits(missing hits) being counted as holes.

Previously the modules that were masked and hence had a hit missing were being counted as holes. This commit allows to use of a different preExec command for masking i.e. --preExec 'ConfigFlags.ITk.doStripModuleVeto = True; ConfigFlags.ITk.JsonPath="path/to/the/json/file"' to be exact. Earlier when any algorithm (other than the ITkStripClusterization) called on 'ITkStripModuleVetoCfg' it found that JsonPath to be empty and that by default meant that no modules were masked, in contrast now they can find the JsonPath to be non-empty.