Merge branch 'ATLASRECTS-6095' into 'master'

Remove FPEs raised from bad muon extensions

See merge request !41926

Event/EventPrimitives/EventPrimitives/EventPrimitivesHelpers.h

 /*
-  Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2021 CERN for the benefit of the ATLAS collaboration
 */
 
 ///////////////////////////////////////////////////////////////////
@@ -29,7 +29,14 @@ namespace Amg {
 inline double error(const Amg::MatrixX& mat, int index) {
     return sqrt(mat(index, index));
 }
-
+/// Returns true if all diagonal elements of the covariance matrix
+/// are greater or equal zero
+template <int N> bool valid_cov(const AmgSymMatrix(N)& mat){
+   for (int i = 0; i < N ; ++i){
+        if (mat(i,i) < 0.) return false;
+   }
+   return true;
+}
 template<int N>
 inline double error(const AmgSymMatrix(N)& mat, int index ) {
     assert(index<N);

MuonSpectrometer/MuonReconstruction/MuonRecTools/MuonTGRecTools/src/MuonSystemExtensionTool.cxx

 /*
-  Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2021 CERN for the benefit of the ATLAS collaboration
 */
 
 #include "MuonSystemExtensionTool.h"
@@ -225,7 +225,7 @@ MuonSystemExtensionTool::muonSystemExtension(const xAOD::TrackParticle&  indetTr
         // create shared pointer and add to garbage collection
         std::shared_ptr<const Trk::TrackParameters> sharedPtr(exPars);
         //    reject intersections with very big uncertainties (parallel to surface)
-        if (Amg::error(*exPars->covariance(), Trk::locX) > 10000.
+        if (!Amg::valid_cov(*exPars->covariance()) || Amg::error(*exPars->covariance(), Trk::locX) > 10000.
             || Amg::error(*exPars->covariance(), Trk::locY) > 10000.)
             continue;