fix: fix tests

Author: salman2013

lms/djangoapps/course_api/serializers.py

@@ -160,7 +160,11 @@ def get_overview(self, course_overview):
         # Note: This makes a call to the modulestore, unlike the other
         # fields from CourseSerializer, which get their data
         # from the CourseOverview object in SQL.
-        return CourseDetails.fetch_about_attribute(course_overview.id, 'overview')
+        overview_value = CourseDetails.fetch_about_attribute(course_overview.id, 'overview')
+
+        # Convert None or empty string to empty dict for consistency
+        # empty string means no template data was found
+        return overview_value or {}
 
     def to_representation(self, instance):
         """

lms/djangoapps/course_api/tests/test_serializers.py

@@ -159,8 +159,11 @@ def setUp(self):
 
         # update the expected_data to include the 'overview' data.
         about_block = XBlock.load_class('about')
-        overview_template = about_block.get_template('overview.yaml')
-        self.expected_data['overview'] = overview_template.get('data')
+        get_template = getattr(about_block, "get_template", None)
+        overview_template = (
+            get_template("overview.yaml") if callable(get_template) else {}
+        )
+        self.expected_data['overview'] = overview_template.get('data', {})
 
     # override test case
     @mock.patch(