Disabling a plugin for an account no longer errors
Disabling a plugin for an account no longer errors

Fixes PLAT-1307

Test Plan:
Enable a plugin at the root account (I recommend github with garbage data)
Try to disable the plugin for an account
  - once when there is no existing settings saved
  - once with existing settings

Change-Id: Ib59981fb8b3f222cf7fe9ff7d356d6e37aec8229
Reviewed-on: https://gerrit.instructure.com/70499
Tested-by: Jenkins
Reviewed-by: Cody Cutrer <c4fe2b1d90ef8f2548c8aeabfa633434316f0305@instructure.com>
QA-Review: August Thornton <9adc7a1161ddf32ff608de792a7e50179545f026@instructure.com>
Product-Review: Brad Horrocks <7b5c5d1f2eba6c540b8e53f17d87a9bd7dbf604b@instructure.com>

sfu/canvas-lms,djbender/canvas-lms,venturehive/canvas-lms,venturehive/canvas-lms,grahamb/canvas-lms,instructure/canvas-lms,roxolan/canvas-lms,venturehive/canvas-lms,matematikk-mooc/canvas-lms,sfu/canvas-lms,matematikk-mooc/canvas-lms,instructure/canvas-lms,HotChalk/canvas-lms,dgynn/canvas-lms,fronteerio/canvas-lms,redconfetti/canvas-lms,instructure/canvas-lms,redconfetti/canvas-lms,sfu/canvas-lms,grahamb/canvas-lms,djbender/canvas-lms,fronteerio/canvas-lms,HotChalk/canvas-lms,grahamb/canvas-lms,SwinburneOnline/canvas-lms,dgynn/canvas-lms,sfu/canvas-lms,roxolan/canvas-lms,grahamb/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,redconfetti/canvas-lms,dgynn/canvas-lms,grahamb/canvas-lms,roxolan/canvas-lms,SwinburneOnline/canvas-lms,instructure/canvas-lms,redconfetti/canvas-lms,djbender/canvas-lms,roxolan/canvas-lms,HotChalk/canvas-lms,matematikk-mooc/canvas-lms,HotChalk/canvas-lms,fronteerio/canvas-lms,sfu/canvas-lms,dgynn/canvas-lms,djbender/canvas-lms,fronteerio/canvas-lms,sfu/canvas-lms,matematikk-mooc/canvas-lms,sfu/canvas-lms,SwinburneOnline/canvas-lms,SwinburneOnline/canvas-lms,instructure/canvas-lms,venturehive/canvas-lms