I am importing data from Bugzilla to Jira. I created some custom fields in Jira to match the ones in Bugzilla. In Bugzilla, some of the custom fields have a default value of '---'. In Jira, I set the default values for those custom fields to be '---' as well. However, after the import the fields that should have a value of '---' show up as empty in Jira. Is there a way to fix this during the import?