FEATURE: backport a minimal String#scrub

BUGFIX: invalid byte sequence in email would explode all processing

app/helpers/application_helper.rb

@@ -25,14 +25,7 @@ module ApplicationHelper
 
   def escape_unicode(javascript)
     if javascript
-      javascript = javascript.dup.force_encoding("utf-8")
-
-      unless javascript.valid_encoding?
-        # work around bust string with a double conversion
-        javascript.encode!("utf-16","utf-8",:invalid => :replace)
-        javascript.encode!("utf-8","utf-16")
-      end
-
+      javascript = javascript.scrub
       javascript.gsub!(/\342\200\250/u, '
')
       javascript.gsub!(/(<\/)/u, '\u003C/')
       javascript.html_safe

lib/email/receiver.rb

@@ -94,10 +94,10 @@ module Email
     end
 
     def discourse_email_parser
-      lines = @body.lines.to_a
+      lines = @body.scrub.lines.to_a
       range_end = 0
 
-      email_year = lines.each_with_index do |l, idx|
+      lines.each_with_index do |l, idx|
         break if l =~ /\A\s*\-{3,80}\s*\z/ ||
                  l =~ Regexp.new("\\A\\s*" + I18n.t('user_notifications.previous_discussion') + "\\s*\\Z") ||
                  (l =~ /via #{SiteSetting.title}(.*)\:$/) ||

lib/freedom_patches/scrub.rb

@@ -0,0 +1,16 @@
+class String
+  # A poor man's scrub, Ruby 2.1 has a much better implementation, but this will do
+  unless method_defined? :scrub
+    def scrub
+      str = dup.force_encoding("utf-8")
+
+      unless str.valid_encoding?
+        # work around bust string with a double conversion
+        str.encode!("utf-16","utf-8",:invalid => :replace)
+        str.encode!("utf-8","utf-16")
+      end
+
+      str
+    end
+  end
+end