attachment_fields_to_save filter doesn't run for attachment saves (w/o alt text set)

[sc0ttkclark]

Currently, 3.5 trunk doesn't run the 'attachment_fields_to_save' filter when you don't set the alt text.

[sc0ttkclark]

Once more, minus compulsive formatting

[nacin]

In 23088:

Fix branchhing in edit_post() where attachment_fields_to_save would only run when the alt text was sent. It should run whenever an attachment is saved. props sc0ttclark. fixes #22774.

[sc0ttkclark]

As I review further, when saving an attachment this filter won't run because it has no attachments in the $post_data[ 'attachments' ]

As it is right now, it appears this won't work in conjunction with the old attachment_fields_to_edit:

​http://www.billerickson.net/wordpress-add-custom-fields-media-gallery/

[nacin]

In the old modal, we were *always* sending back $_POST['attachments'][ ID ][ field ]. In the new modal, there might not be any fields. But we should still run the filter, as get_attachment_fields_to_edit() allowed for raw HTML to be inserted. (FUN.)

has-patch commit remains.

[sc0ttkclark]

This resolves that issue (for backwards compatibility). I'll work on updating everything for the new workflow.

[markjaquith]

In 23094:

Run the attachment_fields_to_save filter even if we don't get the fields we used to get. props nacin. fixes #22774