AA-73 courseware nonetype error

- ensure logic for displaying reset dealines banner in courseware
  is behind the relative dates waffle flag, only shows if the
  course is self paced, and handles the situation where no
  sequentials exist.

lms/djangoapps/courseware/tests/test_views.py

@@ -273,8 +273,8 @@ class IndexQueryTestCase(ModuleStoreTestCase):
     NUM_PROBLEMS = 20
 
     @ddt.data(
-        (ModuleStoreEnum.Type.mongo, 10, 174),
-        (ModuleStoreEnum.Type.split, 4, 172),
+        (ModuleStoreEnum.Type.mongo, 10, 172),
+        (ModuleStoreEnum.Type.split, 4, 170),
     )
     @ddt.unpack
     def test_index_query_counts(self, store_type, expected_mongo_query_count, expected_mysql_query_count):
@@ -2600,6 +2600,7 @@ class TestIndexView(ModuleStoreTestCase):
                 expected_should_show_enroll_button
             )
 
+    @RELATIVE_DATES_FLAG.override(active=True)
     def test_reset_deadlines_banner_is_present_when_viewing_courseware(self):
         user = UserFactory()
         course = CourseFactory.create(self_paced=True)

lms/djangoapps/courseware/views/index.py

@@ -458,17 +458,17 @@ class CoursewareIndex(View):
 
         allow_anonymous = allow_public_access(self.course, [COURSE_VISIBILITY_PUBLIC])
         display_reset_dates_banner = False
-        if not allow_anonymous:  # pylint: disable=too-many-nested-blocks
+        if not allow_anonymous and RELATIVE_DATES_FLAG.is_enabled(self.course.id):  # pylint: disable=too-many-nested-blocks
             course_overview = CourseOverview.objects.get(id=str(self.course_key))
             end_date = getattr(course_overview, 'end_date')
-            if not end_date or timezone.now() < end_date:
+            if course_overview.self_paced and (not end_date or timezone.now() < end_date):
                 if (CourseEnrollment.objects.filter(
                     course=course_overview, user=request.user, mode=CourseMode.VERIFIED
                 ).exists()):
                     course_block_tree = get_course_outline_block_tree(
                         request, str(self.course_key), request.user
                     )
-                    course_sections = course_block_tree.get('children')
+                    course_sections = course_block_tree.get('children', [])
                     for section in course_sections:
                         if display_reset_dates_banner:
                             break