core: remove default value for OperationLog

core/models.py

@@ -1467,10 +1467,7 @@ class OperationLog(models.Model):
         User, related_name="logs", on_delete=models.SET_NULL, null=True
     )
     operation_type = models.CharField(
-        _("operation type"),
-        max_length=40,
-        choices=settings.SITH_LOG_OPERATION_TYPE,
-        default=settings.SITH_LOG_OPERATION_TYPE[0][0],
+        _("operation type"), max_length=40, choices=settings.SITH_LOG_OPERATION_TYPE,
     )
 
     def is_owned_by(self, user):