Fixed error on repository when there are no comments in a changeset (#4126).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@2983 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/helpers/application_helper.rb

@@ -214,7 +214,7 @@ module ApplicationHelper
 
   # Truncates and returns the string as a single line
   def truncate_single_line(string, *args)
-    truncate(string, *args).gsub(%r{[\r\n]+}m, ' ')
+    truncate(string.to_s, *args).gsub(%r{[\r\n]+}m, ' ')
   end
 
   def html_hours(text)