ensure that course_about uses a valid course ID

lms/djangoapps/courseware/views/views.py

@@ -580,12 +580,11 @@ class EnrollStaffView(View):
 
 
 @ensure_csrf_cookie
+@ensure_valid_course_key
 @cache_if_anonymous()
 def course_about(request, course_id):
     """
     Display the course's about page.
-
-    Assumes the course_id is in a valid format.
     """
 
     course_key = SlashSeparatedCourseKey.from_deprecated_string(course_id)