1.0.3dev: Don't show Cc checkbox if user hasn't set their email address in Preferences. Refs #11804.

Instead a hint and link to Preferences in presented.


git-svn-id: http://trac.edgewall.org/intertrac/log:/branches/1.0-stable@13237 af82e41b-90c4-0310-8c96-b1721e28e2e2