Description of problem:
Attempting to access the Systems by Environment generates an error.  Based on the log, this is related to the bulk actions for assigning system groups.

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

How reproducible:
always

Steps to Reproduce:
1. go to Systems -> By Environment
  
Actual results:
error:
    You have a nil object when you didn't expect it! You might have expected an instance of Array. The error occurred while evaluating nil.map

top of stack:

You have a nil object when you didn't expect it!
You might have expected an You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.map
You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.map
#<NoMethodError: You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.map>
/usr/lib/ruby/gems/1.8/gems/actionpack-3.0.10/lib/action_view/helpers/form_options_helper.rb:340:in `options_from_collection_for_select'
/home/bbucking/github/katello/src/app/views/systems/_actions.html.haml:75:in `_app_views_systems__actions_html_haml__1538536810_70058476854740_1358910'
instance of Array.
The error occurred while evaluating nil.map
You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.map
#<NoMethodError: You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.map>
/usr/lib/ruby/gems/1.8/gems/actionpack-3.0.10/lib/action_view/helpers/form_options_helper.rb:340:in `options_from_collection_for_select'
/home/bbucking/github/katello/src/app/views/systems/_actions.html.haml:75:in `_app_views_systems__actions_html_haml__1538536810_70058476854740_1358910'


Expected results:
no error, page rendered properly

Additional info: