prevent "can't modify frozen String" exception when mail sending error (#17235)

git-svn-id: http://svn.redmine.org/redmine/trunk@13198 e93f8b46-1217-0410-a6f0-8f06a7374b81
fix file upload broken on Chrome 36 (#17151)

Contributed by Felix Schäfer.

git-svn-id: http://svn.redmine.org/redmine/trunk@13199 e93f8b46-1217-0410-a6f0-8f06a7374b81