Fixed problem with GET post_id from post editing screen not being recognized.

git-svn-id: https://plugins.svn.wordpress.org/email-users/trunk@946279 b8457f37-d9ea-0310-8a92-e5e31aec5664
Prep for 4.6.10 release.

git-svn-id: https://plugins.svn.wordpress.org/email-users/trunk@946281 b8457f37-d9ea-0310-8a92-e5e31aec5664