Don't error in k5 public course

fixes LS-2814
flag = none

Test plan:
 - Create a k5 course and set it to public visibility
 - Open the course without logging in
 - Expect to see the course content

Change-Id: Icd05f36e9dd476c742520e41ff758969c0ea6449
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/277481
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Robin Kuss <rkuss@instructure.com>
QA-Review: Robin Kuss <rkuss@instructure.com>
Product-Review: Jackson Howe <jackson.howe@instructure.com>

spec/selenium/dashboard/elementary/k5_course_dashboard_student_spec.rb

@@ -93,6 +93,19 @@ describe "student k5 course dashboard" do
       expect(empty_modules_image).to be_displayed
     end
 
+    it 'loads the dashboard for public courses even if unauthenticated' do
+      @subject_course.is_public = true
+      @subject_course.save!
+      destroy_session
+
+      get "/courses/#{@subject_course.id}#home"
+
+      expect(retrieve_title_text).to match(/#{@subject_course_title}/)
+      expect(home_tab).to be_displayed
+      expect(schedule_tab).to be_displayed
+      expect(empty_subject_home).to be_displayed
+    end
+
     it_behaves_like "K5 Subject Home Tab"
   end
 

ui/features/k5_course/index.js

@@ -60,7 +60,7 @@ ready(() => {
         observerList={ENV.OBSERVER_LIST}
         selfEnrollment={ENV.COURSE.self_enrollment}
         tabContentOnly={ENV.TAB_CONTENT_ONLY}
-        currentUserRoles={ENV.current_user_roles}
+        currentUserRoles={ENV.current_user_roles || []}
       />,
       courseContainer
     )