Description of problem:

In preparation for upgrading to CF 5.4, upgraded our Global DB. All appears to be functioning correctly, but when I go to infrastructure -> Virtual machines. I get the following error: 

 Error text:
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undefined method `base_class' for NilClass:Class [vm_infra/explorer]

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[----] I, [2015-08-04T15:09:29.723027 #2591:d01eac]  INFO -- : Started GET "/vm_infra/explorer" for 152.144.161.11 at 2015-08-04 15:09:29 +0100
[----] I, [2015-08-04T15:09:29.734489 #2591:d01eac]  INFO -- : Processing by VmInfraController#explorer as HTML
[----] F, [2015-08-04T15:09:41.128655 #2591:d01eac] FATAL -- : Error caught: [NoMethodError] undefined method `base_class' for NilClass:Class
/var/www/miq/vmdb/app/presenters/tree_builder_vms_and_templates.rb:100:in `block in sort_tree'
/var/www/miq/lib/util/extensions/miq-hash.rb:14:in `each'
/var/www/miq/lib/util/extensions/miq-hash.rb:14:in `sort_by'
/var/www/miq/lib/util/extensions/miq-hash.rb:14:in `sort_by!'
/var/www/miq/vmdb/app/presenters/tree_builder_vms_and_templates.rb:98:in `sort_tree'
/var/www/miq/vmdb/app/presenters/tree_builder_vms_and_templates.rb:95:in `block in sort_tree'
/var/www/miq/vmdb/app/presenters/tree_builder_vms_and_templates.rb:94:in `each'
/var/www/miq/vmdb/app/presenters/tree_builder_vms_and_templates.rb:94:in `sort_tree'
/var/www/miq/vmdb/app/presenters/tree_builder_vms_and_templates.rb:95:in `block in sort_tree'
/var/www/miq/vmdb/app/presenters/tree_builder_vms_and_templates.rb:94:in `each'
/var/www/miq/vmdb/app/presenters/tree_builder_vms_and_templates.rb:94:in `sort_tree'
/var/www/miq/vmdb/app/presenters/tree_builder_vms_and_templates.rb:95:in `block in sort_tree'
/var/www/miq/vmdb/app/presenters/tree_builder_vms_and_templates.rb:94:in `each'
/var/www/miq/vmdb/app/presenters/tree_builder_vms_and_templates.rb:94:in `sort_tree'
/var/www/miq/vmdb/app/presenters/tree_builder_vms_and_templates.rb:95:in `block in sort_tree'
/var/www/miq/vmdb/app/presenters/tree_builder_vms_and_templates.rb:94:in `each'
/var/www/miq/vmdb/app/presenters/tree_builder_vms_and_templates.rb:94:in `sort_tree'
/var/www/miq/vmdb/app/presenters/tree_builder_vms_and_templates.rb:95:in `block in sort_tree'
/var/www/miq/vmdb/app/presenters/tree_builder_vms_and_templates.rb:94:in `each'
/var/www/miq/vmdb/app/presenters/tree_builder_vms_and_templates.rb:94:in `sort_tree'
/var/www/miq/vmdb/app/presenters/tree_builder_vms_and_templates.rb:95:in `block in sort_tree'
/var/www/miq/vmdb/app/presenters/tree_builder_vms_and_templates.rb:94:in `each'
/var/www/miq/vmdb/app/presenters/tree_builder_vms_and_templates.rb:94:in `sort_tree'
/var/www/miq/vmdb/app/presenters/tree_builder_vms_and_templates.rb:95:in `block in sort_tree'
/var/www/miq/vmdb/app/presenters/tree_builder_vms_and_templates.rb:94:in `each



Version-Release number of selected component (if applicable):
5.4.1.0

How reproducible:


Steps to Reproduce:
1. Select Infra-> Virtual Machines
2. 
3.

Actual results:
Get unexpected error

Expected results:
Navigate to VM screen without any problems

Additional info: