In multisite, on a site with only subscribers, wp_dropdown_users returns empty string

[johnjamesjacoby]

This becomes a problem when editing posts on sites with no capable users. Technically, an empty string is the expected result, as the site has no users with adequate capabilities to assign as the author of a post. (I'll propose 1 solution in a comment below.)

To duplicate:

• Setup multisite
• Create a second site
• Add a user to it as a Subscriber
• Remove yourself from that site, if necessary
• Edit the "Hello World" post
• Notice the "Author" metabox is empty

[johnjamesjacoby]

The proposed patch is admittedly not super great, but I think it's an acceptable approach.

If no users on the current site are capable of being listed in the dropdown, (I think) we can safely assume any super administrators are. The attached patch:

• Checks if the call to get_users() returned no results
• Checks if is_multisite()
• Checks if the current logged in user is_super_admin (as only super admins should be able to assign other super admins.)
• Queries for super admins using an approach similar to what's already in: WP_MS_Users_List_Table->prepare_items()