Ensure that random generation parameters are optional

src/scripts/model_maker.py

@@ -371,9 +371,11 @@ def load_model(model_file):
             if (len_vec_x == 0):
                 # Generate random cluster
                 rnd_seed = int(model['system_settings']['rnd_seed'])
+                try:
                     max_rad = float(model['particle_settings']['max_rad'])
-                # random_aggregate() checks internally whether application is INCLUSION
-                #random_aggregate(sconf, gconf, rnd_seed, max_rad)
+                except KeyError:
+                    print("ERROR: random model generation requires specification of particle_settings:max_rad.")
+                    return (None, None)
                 rnd_engine = "COMPACT"
                 try:
                     rnd_engine = model['system_settings']['rnd_engine']
@@ -386,6 +388,7 @@ def load_model(model_file):
                         print("ERROR: compact random generator works only when all sphere types have the same radius.")
                         return (None, None)
                 elif (rnd_engine == "LOOSE"):
+                    # random_aggregate() checks internally whether application is INCLUSION
                     check = random_aggregate(sconf, gconf, rnd_seed, max_rad)
                 else:
                     print("ERROR: unrecognized random generator engine.")