fix JS error adding course to empty subaccount
fix JS error adding course to empty subaccount

if no courses exist, the code that attempts to set up
autocomplete on the course search box instead attaches
to the course name box in the new course dialog

test plan:
 - as an account administrator, create a new subaccount
 - on that account's page (/accounts/X), click the "+ Course"
   button to add a new course
 - typing in the course name  field should not result in
   a JS console error "this.source is not a function"
 - in a subaccount that _does_ have courses, ensure the
   course search autocomplete works in the "Find A Course"
   box on the right

fixes ADMIN-718

Change-Id: Ib68cad88bc329e00b172d8c916edd033d1cfb16a
Reviewed-on: https://gerrit.instructure.com/140708
Tested-by: Jenkins
Reviewed-by: Jon Willesen <0321efbc0acf6204eb6035acb1d418838b450d08@instructure.com>
QA-Review: Jon Willesen <0321efbc0acf6204eb6035acb1d418838b450d08@instructure.com>
Product-Review: Jeremy Stanley <b3f594e10a9edcf5413cf1190121d45078c62290@instructure.com>

sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,djbender/canvas-lms