fixes #334, default group is set to empty value
fixes #334, default group is set to empty value

chef-cookbooks/chef_nginx,periscopedevelopment/nginx,Altiscale/nginx,AudaxHealthInc/nginx,blmlove409/nginx_cookbook,8la/nginx,kri5/nginx,AudaxHealthInc/nginx,AudaxHealthInc/nginx,Sauraus/chef_nginx,miketheman/nginx,kri5/nginx,Roblox/chef_nginx,periscopedevelopment/nginx,Sauraus/chef_nginx,fsultan/nginx,8la/nginx,axos88/chef_nginx,evertrue/nginx-cookbook,axos88/chef_nginx,fsultan/nginx,blmlove409/nginx_cookbook,kri5/nginx,Altiscale/nginx,ffuenf/nginx,evertrue/nginx-cookbook,periscopedevelopment/nginx,cokeboL/nginx,cokeboL/nginx,7bfa689ac3c4be50f8ba6c1ea8c5f316/nginx,axos88/chef_nginx,ttab/nginx,chef-cookbooks/chef_nginx,ffuenf/nginx,luishdez/nginx-cookbook,blmlove409/nginx_cookbook,ttab/nginx,Roblox/chef_nginx,Roblox/chef_nginx,chef-cookbooks/chef_nginx,miketheman/nginx,ffuenf/nginx,luishdez/nginx-cookbook,7bfa689ac3c4be50f8ba6c1ea8c5f316/nginx,miketheman/nginx,cokeboL/nginx,fsultan/nginx,8la/nginx,7bfa689ac3c4be50f8ba6c1ea8c5f316/nginx,evertrue/nginx-cookbook,ttab/nginx,Altiscale/nginx,Sauraus/chef_nginx,luishdez/nginx-cookbook