Fix bug in scoring medium dose.

Query whether region is real (using app->isRealRegion(ir))
before including in medium dose.  Caused segmentation faults
for geometries in which default medium is not defined.

HEN_HOUSE/egs++/ausgab_objects/egs_dose_scoring/egs_dose_scoring.cpp

@@ -290,9 +290,11 @@ void EGS_DoseScoring::reportResults() {
         vector<EGS_Float> massM(nmedia,0);
         int imed = 0;
         for (int ir=0; ir<nreg; ir++) {
+          if(app->isRealRegion(ir)) {
             imed = app->getMedium(ir);
             EGS_Float volume = vol.size() > 1 ? vol[ir]:vol[0];
             massM[imed] += app->getMediumRho(imed)*volume;
+          }
         }
         if (normE==1) {
             egsInformation("\n\n==> Summary of media dosimetry (per particle)\n");