Empty variables definition in the servers block throws ruby error

  "servers": [
    {
      "url": "https://example.production.gw.apicast.io:443",
      "variables": {}
    }
  ],

{:exception=>{:class=>NoMethodError, :message=>"undefined method `map' for nil:NilClass", :backtrace=>["/opt/system/app/lib/three_scale/open_api/url_resolver.rb:23:in `resolve_servers_from_variables'", "/opt/system/app/lib/three_scale/open_api/url_resolver.rb:27:in `resolve_servers_from_variables'", "/opt/system/app/lib/three_scale/open_api/url_resolver.rb:16:in `block in servers'", "/opt/system/app/lib/three_scale/open_api/url_resolver.rb:13:in `map'"]}, :parameters=>{}}