change open file way

lib/sunspot/rich_document.rb

@@ -22,7 +22,7 @@ def add(connection)
 
       @fields.each do |f|
         if f.name.to_s.include?("_attachment") and f.value.present?
-          data = f.value.data
+          data = open(f.value).read rescue ""
           params['fmap.content'] = f.name
         else
           param_name = "literal.#{f.name.to_s}"