Fix warning about catching polymorphic exception by value

dune/microstructure/prestrainedMaterial.hh

@@ -265,7 +265,7 @@ Func2Tensor setupPrestrainPhase(Python::Module module, int phase){
     module.get("phase" + std::to_string(phase) + "_axis").toC<int>(axis);
     module.get("phase" + std::to_string(phase) + "_angle").toC<double>(angle);
   }
-  catch(Dune::Exception)
+  catch(Dune::Exception&)
   {
     //default frame is used.
   }
@@ -329,7 +329,7 @@ Dune::FieldMatrix<double,6,6> setupPhase(Python::Module module, int phase)
     module.get("phase" + std::to_string(phase) + "_axis").toC<int>(axis);
     module.get("phase" + std::to_string(phase) + "_angle").toC<double>(angle);
   }
-  catch(Dune::Exception)
+  catch(Dune::Exception& e)
   {
     // std::cout << "(Could not read frame vectors for material phase) " << phase << ": - Canonical Frame (default) is used." << std::endl;
     std::cout << "(Could not read rotation axis & angle for material phase) " << phase << ": - Canonical Frame (default) is used." << std::endl;