[Positioner] Fix two catches (catch by reference)

owlps-positioner/autocalibrationline.cc

@@ -72,7 +72,7 @@ void AutocalibrationLine::generate_ss()
     {
       trx_rp = &Stock::get_reference_point(trx_cp->get_coordinates()) ;
     }
-  catch (element_not_found e)
+  catch (element_not_found &e)
     {
       ostringstream oss ;
       oss << "No measurements from transmitter CP "

owlps-positioner/topologyreadercsv.cc

@@ -72,7 +72,7 @@ void TopologyReaderCSV::process_area_line()
     {
       building.add_area(area) ;
     }
-  catch (element_already_exists e)
+  catch (element_already_exists &e)
     {
       delete area ;
     }