Item11267: Return error if JSON doesn't decode.

git-svn-id: http://svn.foswiki.org/trunk@17719 0b4bb1d4-4e5a-0410-9cc4-b2b747904278
Item11267: Undefined variable if no commits in message.

git-svn-id: http://svn.foswiki.org/trunk@17720 0b4bb1d4-4e5a-0410-9cc4-b2b747904278