cleanup while preparing for replacement of SimulationAreaDetector

Device/Detector/IDetector.cpp

@@ -232,7 +232,7 @@ std::vector<size_t> IDetector::activeIndices() const
     std::vector<size_t> result;
     for (size_t i = 0; i < sizeOfRegionOfInterest(); ++i)
         if (!detectorMask() || !detectorMask()->isMasked(roiToFullIndex(i), frame()))
-            result.push_back(roiToFullIndex(i));
+            result.push_back(i);
 
     return result;
 }