[chef] Getting this error when using knife command

[dharmesh patel < >]

I have permission to update the cookbook but this error is coming even listing the nodes.

C:\Users\dharmesh.patel\chef-repo\chef-repo\trunk>knife node list

ERROR: You have an error in your config file C:/Users/dharmesh.patel/chef-repo/c

hef-repo/trunk/.chef/knife.rb

TypeError: can't convert nil into String

  C:/Users/dharmesh.patel/chef-repo/chef-repo/trunk/.chef/knife.rb:3:in `initial

ize'

  C:/Users/dharmesh.patel/chef-repo/chef-repo/trunk/.chef/knife.rb:3:in `open'

  C:/Users/dharmesh.patel/chef-repo/chef-repo/trunk/.chef/knife.rb:3:in `from_st

ring'

     # C:/Users/dharmesh.patel/chef-repo/chef-repo/trunk/.chef/knife.rb

  2:

  3: config = YAML::load(File.open(ENV["CHEF_CONFIG"]))

  4: provider = ENV['CHEF_PROVIDER'] || "internal"

--

Thanks & Regards

Dharmesh Patel