Fix thickbox positioning if toolbar is not present.

fixes #26745.

git-svn-id: https://develop.svn.wordpress.org/trunk@27248 602fd350-edb4-49c9-b593-d223f7449a82
Declare $wpdb->base_prefix.

props DavidAnderson.
fixes #16762.


git-svn-id: https://develop.svn.wordpress.org/trunk@27249 602fd350-edb4-49c9-b593-d223f7449a82