Add a function to return an empty string, for filters. props wpsmith, trepmal. fixes #20357.


Built from https://develop.svn.wordpress.org/trunk@25037


git-svn-id: https://core.svn.wordpress.org/trunk@25024 1a063a9b-81f0-0310-95a4-ce76da25c4cd
In populate_network(), insert the first site as blog_id 1, overriding any auto-increment DB seed. props wpmuguru, fixes #16568.


Built from https://develop.svn.wordpress.org/trunk@25038


git-svn-id: https://core.svn.wordpress.org/trunk@25025 1a063a9b-81f0-0310-95a4-ce76da25c4cd