fix diff error in case of line_left out of range.
git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/branches/2.3-stable@11709 e93f8b46-1217-0410-a6f0-8f06a7374b81
fix that diff outputs become ??? in some non ASCII words.
Contributed by Filou Centrinov.
git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/branches/2.3-stable@11551 e93f8b46-1217-0410-a6f0-8f06a7374b81