Description of problem:
Unable to perform chargeback assignments for compute

Version-Release number of selected component (if applicable):
5.9.3

How reproducible:
at customer's environment

Steps to Reproduce:
1. Navigate to Cloud Intel -> Chargeback -> Assignments -> Compute
2. Try to assign to any category then it failed to assign and below exception observed:
[----] I, [2018-10-05T09:43:02.614054 #2204:c68310]  INFO -- :   Parameters: {"id"=>"xx-Compute"}
[----] F, [2018-10-05T09:43:03.237975 #2204:c68310] FATAL -- : Error caught: [NoMethodError] undefined method `[]' for nil:NilClass
/opt/rh/cfme-gemset/bundler/gems/cfme-ui-classic-ffe20d38326d/app/controllers/chargeback_controller.rb:717:in `block in cb_assign_set_form_vars'
/opt/rh/cfme-gemset/bundler/gems/cfme-ui-classic-ffe20d38326d/app/controllers/chargeback_controller.rb:713:in `each'
/opt/rh/cfme-gemset/bundler/gems/cfme-ui-classic-ffe20d38326d/app/controllers/chargeback_controller.rb:713:in `cb_assign_set_form_vars'
/opt/rh/cfme-gemset/bundler/gems/cfme-ui-classic-ffe20d38326d/app/controllers/chargeback_controller.rb:402:in `get_node_info'
/opt/rh/cfme-gemset/bundler/gems/cfme-ui-classic-ffe20d38326d/app/controllers/chargeback_controller.rb:41:in `tree_select'
/opt/rh/cfme-gemset/gems/actionpack-5.0.6/lib/action_controller/metal/basic_implicit_render.rb:4:in `send_action'
                                                                                                                  

Actual results:

It is throwing exception, it is expecting two parameters i.e. source and rate type but in compute it is providing only rate type but no source information due to which it is throwing above exception.

Expected results:

It should set chargeback rate based on compute rate type.

Additional info: