Description of problem:
ApplicationsController#index raised the exception NoMethodError: undefined method `is_sparse?'

Stacktrace:
…gin-controller-1.18.4/app/models/
component_instance.rb:  31:in `is_sparse?'
…ller-1.18.4/app/rest_models/
rest_embedded_cartridge.rb: 134:in `initialize'
…gin-controller-1.18.4/app/helpers/
rest_model_helper.rb:  85:in `new'
…gin-controller-1.18.4/app/helpers/
rest_model_helper.rb:  85:in `get_embedded_rest_cartridge'
…gin-controller-1.18.4/app/helpers/
rest_model_helper.rb:  55:in `block (2 levels) in get_application_rest_cartridges'
…s/gems/mongoid-3.0.21/lib/mongoid/contextual/
memory.rb: 121:in `block in each'
…s/gems/mongoid-3.0.21/lib/mongoid/contextual/
memory.rb: 120:in `each'
…s/gems/mongoid-3.0.21/lib/mongoid/contextual/
memory.rb: 120:in `each'
…are/gems/gems/mongoid-3.0.21/lib/mongoid/
contextual.rb:  18:in `each'
…gin-controller-1.18.4/app/helpers/
rest_model_helper.rb:  51:in `block in get_application_rest_cartridges'
…gin-controller-1.18.4/app/helpers/
rest_model_helper.rb:  49:in `each'
…gin-controller-1.18.4/app/helpers/
rest_model_helper.rb:  49:in `get_application_rest_cartridges'
…gin-controller-1.18.4/app/helpers/
rest_model_helper.rb:  40:in `get_rest_application'
…ller-1.18.4/app/controllers/
applications_controller.rb:  21:in `block in index'
…ms/gems/mongoid-3.0.21/lib/mongoid/contextual/
mongo.rb: 577:in `yield_document'
…ms/gems/mongoid-3.0.21/lib/mongoid/contextual/
mongo.rb: 133:in `block (2 levels) in each'
…ms/gems/mongoid-3.0.21/lib/mongoid/contextual/
mongo.rb: 132:in `each'
…ms/gems/mongoid-3.0.21/lib/mongoid/contextual/
mongo.rb: 132:in `block in each'
…ms/gems/mongoid-3.0.21/lib/mongoid/contextual/
mongo.rb: 556:in `selecting'
…ms/gems/mongoid-3.0.21/lib/mongoid/contextual/
mongo.rb: 131:in `each'
…are/gems/gems/mongoid-3.0.21/lib/mongoid/
contextual.rb:  18:in `each'
…ller-1.18.4/app/controllers/
applications_controller.rb:  21:in `map'
…ller-1.18.4/app/controllers/
applications_controller.rb:  21:in `index'
…ntroller-1.18.4/lib/openshift/controller/
action_log.rb:  80:in `set_logged_request'
…sr/share/gems/gems/journey-1.0.4/lib/journey/
router.rb:  68:in `block in call'
…sr/share/gems/gems/journey-1.0.4/lib/journey/
router.rb:  56:in `each'
…sr/share/gems/gems/journey-1.0.4/lib/journey/
router.rb:  56:in `call'
…per-0.11.1/lib/mongo_mapper/middleware/
identity_map.rb:  10:in `call'
…oid-3.0.21/lib/rack/mongoid/middleware/
identity_map.rb:  34:in `block in call'
…e/gems/gems/mongoid-3.0.21/lib/mongoid/
unit_of_work.rb:  39:in `unit_of_work'
…oid-3.0.21/lib/rack/mongoid/middleware/
identity_map.rb:  34:in `call'
…3/root/usr/share/gems/gems/rack-1.4.1/lib/rack/
etag.rb:  23:in `call'
…/share/gems/gems/rack-1.4.1/lib/rack/
conditionalget.rb:  25:in `call'
…e/gems/gems/rack-1.4.1/lib/rack/session/abstract/
id.rb: 205:in `context'
…e/gems/gems/rack-1.4.1/lib/rack/session/abstract/
id.rb: 200:in `call'
…/share/gems/gems/rack-1.4.1/lib/rack/
methodoverride.rb:  21:in `call'
…oot/usr/share/gems/gems/rack-1.4.1/lib/rack/
runtime.rb:  17:in `call'
…3/root/usr/share/gems/gems/rack-1.4.1/lib/rack/
lock.rb:  15:in `call'
…are/gems/gems/rack-cache-1.2/lib/rack/cache/
context.rb: 136:in `forward'
…are/gems/gems/rack-cache-1.2/lib/rack/cache/
context.rb: 245:in `fetch'
…are/gems/gems/rack-cache-1.2/lib/rack/cache/
context.rb: 185:in `lookup'
…are/gems/gems/rack-cache-1.2/lib/rack/cache/
context.rb:  66:in `call!'
…are/gems/gems/rack-cache-1.2/lib/rack/cache/
context.rb:  51:in `call'
…r-3.0.21/lib/phusion_passenger/rack/
request_handler.rb:  97:in `process_request'
…0.21/lib/phusion_passenger/
abstract_request_handler.rb: 521:in `accept_and_process_next_request'
…0.21/lib/phusion_passenger/
abstract_request_handler.rb: 274:in `main_loop'
…0.21/lib/phusion_passenger/rack/
application_spawner.rb: 206:in `start_request_handler'
…0.21/lib/phusion_passenger/rack/
application_spawner.rb:  79:in `block in spawn_application'
…s/gems/passenger-3.0.21/lib/phusion_passenger/
utils.rb: 470:in `safe_fork'
…0.21/lib/phusion_passenger/rack/
application_spawner.rb:  64:in `spawn_application'
…assenger-3.0.21/lib/phusion_passenger/
spawn_manager.rb: 264:in `spawn_rack_application'
…assenger-3.0.21/lib/phusion_passenger/
spawn_manager.rb: 137:in `spawn_application'
…assenger-3.0.21/lib/phusion_passenger/
spawn_manager.rb: 275:in `handle_spawn_application'
…senger-3.0.21/lib/phusion_passenger/
abstract_server.rb: 357:in `server_main_loop'
…senger-3.0.21/lib/phusion_passenger/
abstract_server.rb: 206:in `start_synchronously'

Version-Release number of selected component (if applicable):
Found in PROD

How reproducible:
Reported 50+ times in PROD in last 7 days.