spec: add proper error condition
spec: add proper error condition

This makes it so that when the error branch is called in the
app code, it doesn't throw a error because errors is undefined

This should prevent errors like MASTER-JAVASCRIPT-BUILD-B from
happening in Sentry.

refs CORE-1563

Test Plan:
  - Run `yarn run jspec ./spec/javascripts/jsx/shared/MessageStudentsSpec.js`
  - You should see nothing about forEach of undefined

Change-Id: Ib9eeed45e830835222d451475395c79f9554985e
Reviewed-on: https://gerrit.instructure.com/154813
Tested-by: Jenkins
Reviewed-by: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>
Product-Review: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>
QA-Review: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>

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