Convert to bound state also on empty sensitive surfaces.

This allows to merge retrieval of source link ranges, measurement
selection and track state creation into one unit.

This increases the computational effort slightly for empty, sensitive
surfaces, since the computation of bound states is slightly more
demanding than the computation of curvilinear states, but for complex
events like HL-LHC events the degradation was not measurable.

Core/include/Acts/TrackFinding/CombinatorialKalmanFilter.hpp

@@ -747,7 +747,7 @@ class CombinatorialKalmanFilter {
       }
 
       // Transport the covariance to the surface
-      if (isHole || isMaterialOnly) {
+      if (isMaterialOnly) {
         stepper.transportCovarianceToCurvilinear(state.stepping);
       } else {
         stepper.transportCovarianceToBound(state.stepping, *surface);