JSON Parse error Unrecognized token '<' parse@[native code]

I have a problem with http://ift.tt/17HJBBx. It works perfect in localhost but deployed on Firebase there is a bug common to all login (email, Google or Facebook) The bug is here https://artadysgouv.fr and is: "JSON Parse error: Unrecognized token '<' parse@[native code]" .