Cloned from https://bugzilla.redhat.com/show_bug.cgi?id=1113012
Description of problem:
I was trying to create a new host, and I selected the hostgroup from dropdown. Later I unselected the hostgroup by selecting a empty row there and then Firebug raises error:

"NetworkError: 404 Not Found - https://dhcp207-190.lab.eng.pnq.redhat.com/hosts/process_hostgroup"

Version-Release number of selected component (if applicable):
sat6 beta snap10 compose3

How reproducible:
always

Steps to Reproduce:
1. create a hostgroup
2. while creating new host, select hostgroup from down and then unselect it by selecting empty row from drop down
3.

Actual results:

Expected results:
no error should be raised on selecting empty row to unselect the previous selection

Additional info:
log from production.log:

Processing by HostsController#process_hostgroup as */*
Parameters: {"utf8"=>"✓", "authenticity_token"=>"/P7i8eyaFGfuUe8/6uOXt6kv8lh8YdzzQ/U1UkONi8s=", "host"=>{"name"=>"shost", "organization_id"=>"1", "location_id"=>"2", "hostgroup_id"=>"", "compute_resource_id"=>"1", "environment_id"=>"3", "content_source_id"=>"1", "puppet_ca_proxy_id"=>"", "puppet_proxy_id"=>"", "puppetclass_ids"=>[""], "managed"=>"true", "progress_report_id"=>"[FILTERED]", "type"=>"Host::Managed", "compute_attributes"=>{"cpus"=>"1", "memory"=>"805306368", "nics_attributes"=>{"new_nics"=>{"type"=>"bridge", "_delete"=>"", "bridge"=>"eth0", "model"=>"virtio"}, "0"=>{"type"=>"bridge", "_delete"=>"", "bridge"=>"eth0", "model"=>"virtio"}}, "volumes_attributes"=>{"new_volumes"=>{"pool_name"=>"default", "capacity"=>"10G", "allocation"=>"0G", "format_type"=>"raw", "_delete"=>""}, "0"=>{"pool_name"=>"default", "capacity"=>"10G", "allocation"=>"0G", "format_type"=>"raw", "_delete"=>""}}, "start"=>"1"}, "domain_id"=>"2", "realm_id"=>"", "mac"=>"", "subnet_id"=>"1", "ip"=>"192.168.100.3", "interfaces_attributes"=>{"new_interfaces"=>{"_destroy"=>"false", "type"=>"Nic::Managed", "mac"=>"", "name"=>"", "domain_id"=>"", "ip"=>"", "provider"=>"IPMI"}}, "architecture_id"=>"1", "operatingsystem_id"=>"1", "provision_method"=>"build", "build"=>"1", "ptable_id"=>"7", "disk"=>"", "root_pass"=>"[FILTERED]", "is_owned_by"=>"1-Users", "enabled"=>"1", "comment"=>"", "overwrite"=>"false"}, "kt_environment_id"=>"ACME_Corporation/Dev", "capabilities"=>"build image", "provider"=>"Libvirt"}
Completed 404 Not Found in 32ms (ActiveRecord: 3.4ms)