Avoid PHP notices in Media Library if an attachment parent post type no longer exists.

props wpsmith.
fixes #27439.
Built from https://develop.svn.wordpress.org/trunk@27560


git-svn-id: http://core.svn.wordpress.org/trunk@27403 1a063a9b-81f0-0310-95a4-ce76da25c4cd
In Recent Posts widget set default number to 5.

props afercia.
fixes #27417.
Built from https://develop.svn.wordpress.org/trunk@27561


git-svn-id: http://core.svn.wordpress.org/trunk@27404 1a063a9b-81f0-0310-95a4-ce76da25c4cd