gets error when using try, but works fine without try - ruby-on-rails

Question

I have this line in my code:
student.user.try(:services).try( :where, {course_id: params[:current_course]} ).try(:first)
It gives the following error:
undefined method `where' for #<Array:0x007fc35070da30>
But when I use it without try like this:
student.user.try(:services).where("course_id = ?", params[:current_course] ).try(:first)
everything is OK.
What's the problem with try?
Per your request adding the backtrace:
activesupport (3.2.8) lib/active_support/core_ext/object/try.rb:36:in `try'
activerecord (3.2.8) lib/active_record/associations/collection_proxy.rb:89:in `method_missing'
app/controllers/trainings_controller.rb:926:in `block in transfer_students'
app/controllers/trainings_controller.rb:922:in `each'
app/controllers/trainings_controller.rb:922:in `transfer_students'
actionpack (3.2.8) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
actionpack (3.2.8) lib/abstract_controller/base.rb:167:in `process_action'
actionpack (3.2.8) lib/action_controller/metal/rendering.rb:10:in `process_action'
actionpack (3.2.8) lib/abstract_controller/callbacks.rb:18:in `block in process_action'
activesupport (3.2.8) lib/active_support/callbacks.rb:491:in `_run__1196091745092505907__process_action__2696008159292751787__callbacks'
activesupport (3.2.8) lib/active_support/callbacks.rb:405:in `__run_callback'
activesupport (3.2.8) lib/active_support/callbacks.rb:385:in `_run_process_action_callbacks'
activesupport (3.2.8) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.2.8) lib/abstract_controller/callbacks.rb:17:in `process_action'
actionpack (3.2.8) lib/action_controller/metal/rescue.rb:29:in `process_action'
actionpack (3.2.8) lib/action_controller/metal/instrumentation.rb:30:in `block in process_action'
activesupport (3.2.8) lib/active_support/notifications.rb:123:in `block in instrument'
activesupport (3.2.8) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
activesupport (3.2.8) lib/active_support/notifications.rb:123:in `instrument'
actionpack (3.2.8) lib/action_controller/metal/instrumentation.rb:29:in `process_action'
actionpack (3.2.8) lib/action_controller/metal/params_wrapper.rb:207:in `process_action'
activerecord (3.2.8) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
actionpack (3.2.8) lib/abstract_controller/base.rb:121:in `process'
actionpack (3.2.8) lib/abstract_controller/rendering.rb:45:in `process'
actionpack (3.2.8) lib/action_controller/metal.rb:203:in `dispatch'
actionpack (3.2.8) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'

Answer 1

Moving this to an answer since it seemed to be helpful.
Reading the release notes, this seems to be the legacy behavior of Object.try. It was changed to the current expectation in Rails 4:
"Object#try will now return nil instead of raise a NoMethodError if the receiving object does not implement the method"
Rails 4.0 Release notes