Fixed: error raised when copying project wiki with wiki module disabled (#13097).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11332 e93f8b46-1217-0410-a6f0-8f06a7374b81
Test failures from r11331 (#13075).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11333 e93f8b46-1217-0410-a6f0-8f06a7374b81