[support] SQL Error on Update to D6

I am beginning to work on upgrading a large site to D6. I thus far just took the D6 files, with nothing else, and pointed it to a copy of the DB and ran update. This is the error I received:

· warning: mysql_query() [http://www.mysql.com/doc]: Column 'uid' cannot be null in \ApacheRoot\TestDrupal6\includes\database.mysql.inc on line 108. · user warning: Column 'uid' cannot be null query: UPDATE files SET uid = (SELECT n.uid FROM node n WHERE files.uid = n.nid) in \ApacheRoot\TestDrupal6\modules\system\system.install on line 1954.

I had a few of these, maybe only 2.

Anyhow know what this is? My guess is that it could be ignored, but I'm not 100% sure.

Thanks