FIx PHP warning when saving a post without a topic

git-svn-id: http://plugins.svn.wordpress.org/bbpress-post-topics/trunk@749498 b8457f37-d9ea-0310-8a92-e5e31aec5664
Bug fixes for draft settings

git-svn-id: http://plugins.svn.wordpress.org/bbpress-post-topics/trunk@749621 b8457f37-d9ea-0310-8a92-e5e31aec5664
Updating translations; updating trunk to 1.8 and bumping version num

git-svn-id: http://plugins.svn.wordpress.org/bbpress-post-topics/trunk@751131 b8457f37-d9ea-0310-8a92-e5e31aec5664