ActsEventCnv: make it possible to run without TrackingGeometryTool for Muon tests

As per the description, this is necessary for !71240 (merged) but since it's independent, let's make it its own MR.

Should not impact any other tests, nor is it running in any production setting.

Tracking/Acts/ActsConfig/python/ActsEventCnvConfig.py

@@ -8,9 +8,12 @@ def ActsToTrkConverterToolCfg(flags,
                               **kwargs) -> ComponentAccumulator:
     acc = ComponentAccumulator()
 
-    if 'TrackingGeometryTool' not in kwargs:
+    # Currently this does not work if we are in a muon-only mode
+    if flags.Detector.GeometryITk and 'TrackingGeometryTool' not in kwargs:
         from ActsConfig.ActsGeometryConfig import ActsTrackingGeometryToolCfg
         kwargs.setdefault("TrackingGeometryTool", acc.popToolsAndMerge(ActsTrackingGeometryToolCfg(flags)))
+    else:
+         kwargs.setdefault("TrackingGeometryTool", "")
 
     acc.setPrivateTools(CompFactory.ActsTrk.ActsToTrkConverterTool(name, **kwargs))
     return acc