Pass model to create_internal_objects not grid

gprMax/contexts.py

@@ -106,7 +106,7 @@ class Context:
         if not model_config.reuse_geometry():
             scene = self._get_scene(model_num)
             model = self._create_model()
-            scene.create_internal_objects(model.G)
+            scene.create_internal_objects(model)
 
         model.build()
 

gprMax/scene.py

@@ -138,12 +138,14 @@ class Scene:
 
         self.process_cmds(cmds_unique, G)
 
-    def create_internal_objects(self, G):
+    def create_internal_objects(self, model: Model):
         """Calls the UserObject.build() function in the correct way - API
         presents the user with UserObjects in order to build the internal
         Rx(), Cylinder() etc... objects.
         """
 
+        G = model.G
+
         # Create pre-defined (built-in) materials
         create_built_in_materials(G)