Vmware default folder in provisioning

I have been able to define vlans in provision dialog that users can select on provisioning like this:

:description: Network
test-lan: test-lan
test-lan2: test-lan2
:description: vLan
:required: true
:display: :edit
:data_type: :string

But how do you define vmware folders that users can select in provisioning dialog? I tried to do it the same way but the automation fails with [NoMethodError]: undefined method `name’ for nil:NilClass