How to create pivot table containing some empty values?

Hello. I've got a problem. I have a logfile. And I would like to create a pivot table (url, referer) and export it to csv. But there is one problem: some refs are empty. Then splunk.... exports only these rows where ref is not empty. So, instead of including all rows, the exported CSV contains only ~5%, How to fix it? Thank you in advance for your help