Fix error when rendering XBlock in preview

apps/submissions/api.py

@@ -252,8 +252,13 @@ def get_score(student_item):
         }]
 
     """
-    student_item_model = StudentItem.objects.get(**student_item)
-    scores = Score.objects.filter(student_item=student_item_model)
+    try:
+        student_item_model = StudentItem.objects.get(**student_item)
+        scores = Score.objects.filter(student_item=student_item_model)
+
+    except StudentItem.DoesNotExist:
+        return None
+
     return ScoreSerializer(scores, many=True).data
 
 

apps/submissions/tests/test_api.py

 import datetime
+import copy
 
 from ddt import ddt, file_data
 from django.db import DatabaseError
@@ -134,6 +135,11 @@ class TestApi(TestCase):
         scores = api.get_score(STUDENT_ITEM)
         self._assert_score(scores[0], 11, 12)
 
+    def test_get_score_no_student_id(self):
+        student_item = copy.deepcopy(STUDENT_ITEM)
+        student_item['student_id'] = None
+        self.assertIs(api.get_score(student_item), None)
+
     def _assert_score(
             self,
             score,
@@ -141,4 +147,4 @@ class TestApi(TestCase):
             expected_points_possible):
         self.assertIsNotNone(score)
         self.assertEqual(score["points_earned"], expected_points_earned)
-        self.assertEqual(score["points_possible"], expected_points_possible)
\ No newline at end of file
+        self.assertEqual(score["points_possible"], expected_points_possible)