2.2.1 is no longer raising JWT::DecodeError on nil verification key

[jamesstonehill]

This raises no implicit conversion of nil into String (TypeError)

require "bundler/inline"

gemfile do
  gem "jwt", "2.2.1"
end

token = JWT.encode({}, "foo")

JWT.decode(token, nil, true)

This raises No verification key available (JWT::DecodeError))

require "bundler/inline"

gemfile do
  gem "jwt", "2.1.0"
end

token = JWT.encode({}, "foo")

JWT.decode(token, nil, true)

I'm guessing we still want to be raising the No verification key available (JWT::DecodeError)) key since it's a clearer message.