Fixed a bug whereby a file type with multiple mime types but no official type

would cause the best_content_type to throw an error on trying nil.content_type.

lib/paperclip/io_adapters/file_adapter.rb

@@ -65,7 +65,12 @@ module Paperclip
     end
 
     def best_content_type_option(types)
-      types.reject {|type| type.content_type.match(/\/x-/) }.first.content_type
+      best = types.reject {|type| type.content_type.match(/\/x-/) }
+      if best.size == 0
+        types.first.content_type
+      else
+        best.first.content_type
+      end
     end
 
     def type_from_file_command

test/io_adapters/file_adapter_test.rb

@@ -60,6 +60,16 @@ class FileAdapterTest < Test::Unit::TestCase
         end
       end
 
+      context "file with multiple possible x-types but no official type" do
+        setup do
+          MIME::Types.stubs(:type_for).returns([MIME::Type.new('image/x-mp4'), MIME::Type.new('image/x-video')])
+        end
+
+        should "return the last" do
+          assert_equal "image/x-mp4", @subject.content_type
+        end
+      end
+
       context "file with content type derived from file command on *nix" do
         setup do
           MIME::Types.stubs(:type_for).returns([])