Don't allow themes without a style.css editor to be edited. These themes are...

Don't allow themes without a style.css editor to be edited. These themes are too broken to be salvaged by the theme editor. see #20103.



git-svn-id: https://core.svn.wordpress.org/trunk@20557 1a063a9b-81f0-0310-95a4-ce76da25c4cd