heroku 命令错误 不知道为什么

xxx[@ubuntu](/user/ubuntu):~$ heroku login
/usr/local/heroku/vendor/gems/json-1.7.7/lib/json/common.rb:67:in `initialize': no implicit conversion of nil into Hash (TypeError)
	from /usr/local/heroku/vendor/gems/json-1.7.7/lib/json/common.rb:67:in `new'
	from /usr/local/heroku/vendor/gems/json-1.7.7/lib/json/common.rb:67:in `generator='
	from /usr/local/heroku/vendor/gems/json-1.7.7/lib/json/ext.rb:17:in `<module:Ext>'
	from /usr/local/heroku/vendor/gems/json-1.7.7/lib/json/ext.rb:12:in `<module:JSON>'
	from /usr/local/heroku/vendor/gems/json-1.7.7/lib/json/ext.rb:9:in `<top (required)>'
	from /usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:51:in `require'
	from /usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:51:in `require'
	from /usr/local/heroku/vendor/gems/json-1.7.7/lib/json.rb:58:in `<module:JSON>'
	from /usr/local/heroku/vendor/gems/json-1.7.7/lib/json.rb:54:in `<top (required)>'
	from /usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:51:in `require'
	from /usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:51:in `require'
	from /usr/local/heroku/lib/heroku/cli.rb:18:in `<top (required)>'
	from /usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:51:in `require'
	from /usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:51:in `require'
	from /usr/local/heroku/bin/heroku:23:in `<main>'