Attachment fu’s “Size is not in the list” problem

The fix is to specify :min_size config for has_attachment call:

 has_attachment :content_type => :image,
                 :storage => :file_system,
                 :max_size => 10.megabytes,
         :min_size => 0.kilobytes,
         :resize_to => ‘320×320>’,
                 :thumbnails => { :thumb => ‘126×126>’ }