Lion Server: Server app unable to display Profile Manager settings after updating to Lion Server v10.7.3

Additional Information

If you encounter the issue described in this article, the /var/log/devicemgr/profilemanager.log file will show a backtrace such as this:

(timestamp) pm.example.com ProfileManager[8023] <Error>: ServermgrDevicemgr: Exception caught undefined method `delete' for nil:NilClass:
/usr/share/devicemgr/backend/app/models/interface_knob_set.rb:81:in `generate_payload_hash'
/usr/share/devicemgr/backend/lib/profile_manager.rb:506:in `generate_profile_section_hash'
/usr/share/devicemgr/backend/lib/profile_manager.rb:448:in `generate_profile'
/usr/share/devicemgr/backend/vendor/rails/activerecord/lib/active_record/associations/association_collection.rb:392:in `method_missing'
/usr/share/devicemgr/backend/vendor/rails/activerecord/lib/active_record/associations/association_proxy.rb:215:in `each'
/usr/share/devicemgr/backend/vendor/rails/activerecord/lib/active_record/associations/association_proxy.rb:215:in `send'
/usr/share/devicemgr/backend/vendor/rails/activerecord/lib/active_record/associations/association_proxy.rb:215:in `method_missing'
/usr/share/devicemgr/backend/vendor/rails/activerecord/lib/active_record/associations/association_collection.rb:392:in `method_missing'
/usr/share/devicemgr/backend/lib/profile_manager.rb:446:in `generate_profile'
/usr/share/devicemgr/backend/lib/servermgr_devicemgr.rb:118:in `readSettings'
/usr/share/devicemgr/backend/lib/servermgr_devicemgr.rb:44:in `send'
/usr/share/devicemgr/backend/lib/servermgr_devicemgr.rb:44:in `run'
/usr/share/devicemgr/backend/lib/servermgr_devicemgr.rb:376
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/rubygems/custom_require.rb:31:in `eval'
/usr/share/devicemgr/backend/vendor/rails/railties/lib/commands/runner.rb:46
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/rubygems/custom_require.rb:31:in `require'
/usr/share/devicemgr/backend/script/runner:3