NoMethodError: undefined method `with_indifferent_access' for []:Array

[zhaohanweng]

/vendor/bundle/jruby/1.9/gems/fb_graph-2.7.8/lib/fb_graph/node.rb:147 in "handle_response" 
/vendor/bundle/jruby/1.9/gems/fb_graph-2.7.8/lib/fb_graph/node.rb:49 in "get" 
/vendor/bundle/jruby/1.9/gems/fb_graph-2.7.8/lib/fb_graph/node.rb:19 in "fetch" 

This is a very rare case. We have the code that does the search query using the gem, most of the time it will return { 'data': [] }. But there's still a chance that the response.body will be "[]" instead of json. I filed a bug on facebook, they said everything is fine. Its very hard to produce this, this error occurs maybe 1 in 1000 calls.
Maybe this is caused by http_client?