fix null file descriptor error
fix null file descriptor error

tas50/packer,paulmey/packer,mitchellh/packer,tas50/packer,grubernaut/packer,rnaveiras/packer,tas50/packer,bryson/packer,dave2/packer,rnaveiras/packer,timsutton/packer,bryson/packer,rnaveiras/packer,hashicorp/packer,mitchellh/packer,timsutton/packer,rnaveiras/packer,timsutton/packer,pecigonzalo/packer,dave2/packer,ricardclau/packer,rnaveiras/packer,hashicorp/packer,paulmey/packer,grubernaut/packer,tas50/packer,grubernaut/packer,hashicorp/packer,rnaveiras/packer,tas50/packer,ricardclau/packer,pecigonzalo/packer,timsutton/packer,dave2/packer,paulmey/packer,mitchellh/packer,bryson/packer,hashicorp/packer,bryson/packer,paulmey/packer,grubernaut/packer,pecigonzalo/packer,paulmey/packer,mitchellh/packer,ricardclau/packer,mitchellh/packer,bryson/packer,ricardclau/packer,pecigonzalo/packer,dave2/packer,dave2/packer,timsutton/packer,timsutton/packer,dave2/packer,grubernaut/packer,tas50/packer,ricardclau/packer,ricardclau/packer,paulmey/packer,grubernaut/packer,bryson/packer