* catch an exception by references, otherwise g++ issues warning

  in version 9 [rtj]

Author: rjones30

src/AdaptiveSampler.cc

@@ -748,7 +748,7 @@ int AdaptiveSampler::mergeState(const std::string filename)
       fMaximum_cells = keyval.at("fMaximum_cells");
       fEfficiency_target = keyval.at("fEfficiency_target");
    }
-   catch (std::exception e) {
+   catch (std::exception &e) {
       std::cerr << "AdaptiveSampler::mergeState warning - "
                 << "required keyword missing in " << filename
                 << std::endl;

src/GlueXSteppingAction.cc

@@ -219,7 +219,7 @@ void GlueXSteppingAction::UserSteppingAction(const G4Step* step)
       try {
          proftree = bgprofiles.at(det);
       }
-      catch(std::out_of_range err) {
+      catch(std::out_of_range &err) {
          std::stringstream names;
          names << "det" << det;
          std::stringstream titles;