Top phrase is a blank entry

in webtrends report

[fom2001uk]

For the second month running, one of our sites is showing the top phrase searched for as blank in the webtrends report.

I've never seen this before. NetIQ has nothing about it in their knowledge base.

Does anyone know what this means?

[carguy84]

A site search or coming in from the search engines?

[fom2001uk]

It's in the top phrases section (external referrals from search engines).

How can it be blank? I know this another webtrends glitch, but I'd really like to have it explained.