fix back-button on description diff page in case of no browser history (#13697)

Contributed by Filou Centrinov.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11893 e93f8b46-1217-0410-a6f0-8f06a7374b81
remove unneeded escaping at app/views/journals/diff.html.erb

Rails3 escapes by default.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11894 e93f8b46-1217-0410-a6f0-8f06a7374b81