Fix model_class lookup

Author: bctiemann

netbox_custom_objects/models.py

@@ -417,7 +417,7 @@ def __str__(self):
     @property
     def model_class(self):
         if self.related_object_type.app_label == 'netbox_custom_objects':
-            return apps.get_model(self.related_object_type.app_label, 'customobjecttype')
+            return apps.get_model(self.related_object_type.app_label, 'customobject')
         return apps.get_model(self.related_object_type.app_label, self.related_object_type.model)
 
     @property