Prevents calling #truncate on nil.

git-svn-id: http://svn.redmine.org/redmine/trunk@13897 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/helpers/application_helper.rb

@@ -397,7 +397,7 @@ module ApplicationHelper
   end
 
   def truncate_single_line_raw(string, length)
-    string.truncate(length).gsub(%r{[\r\n]+}m, ' ')
+    string.to_s.truncate(length).gsub(%r{[\r\n]+}m, ' ')
   end
 
   # Truncates at line break after 250 characters or options[:length]