scm: return if str.blank? in to_utf8(str).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@4960 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/helpers/repositories_helper.rb

@@ -117,6 +117,7 @@ module RepositoriesHelper
   end
   
   def to_utf8(str)
+    return str if str.blank?
     if str.respond_to?(:force_encoding)
       str.force_encoding('UTF-8')
     else

app/models/changeset.rb

@@ -247,6 +247,7 @@ class Changeset < ActiveRecord::Base
   end
 
   def self.to_utf8(str)
+    return str if str.blank?
     encoding = Setting.commit_logs_encoding.to_s.strip
     unless encoding.blank? || encoding == 'UTF-8'
       begin