Add check for nil before converting HTML

git-svn-id: http://ios.svn.wordpress.org/trunk@4055 7d847f7c-ffe1-4a24-85be-b788d016d96a
Fix crash when updating notification comment thread

git-svn-id: http://ios.svn.wordpress.org/trunk@4056 7d847f7c-ffe1-4a24-85be-b788d016d96a
Fix crash when getting post formats

git-svn-id: http://ios.svn.wordpress.org/trunk@4057 7d847f7c-ffe1-4a24-85be-b788d016d96a