fix: issue serializer to remove deleted labels and assignees (#6241)

apiserver/plane/api/serializers/issue.py

@@ -237,17 +237,37 @@ def to_representation(self, instance):
                 from .user import UserLiteSerializer
 
                 data["assignees"] = UserLiteSerializer(
-                    instance.assignees.all(), many=True
+                    User.objects.filter(
+                        pk__in=IssueAssignee.objects.filter(issue=instance).values_list(
+                            "assignee_id", flat=True
+                        )
+                    ),
+                    many=True,
                 ).data
             else:
                 data["assignees"] = [
-                    str(assignee.id) for assignee in instance.assignees.all()
+                    str(assignee)
+                    for assignee in IssueAssignee.objects.filter(
+                        issue=instance
+                    ).values_list("assignee_id", flat=True)
                 ]
         if "labels" in self.fields:
             if "labels" in self.expand:
-                data["labels"] = LabelSerializer(instance.labels.all(), many=True).data
+                data["labels"] = LabelSerializer(
+                    Label.objects.filter(
+                        pk__in=IssueLabel.objects.filter(issue=instance).values_list(
+                            "label_id", flat=True
+                        )
+                    ),
+                    many=True,
+                ).data
             else:
-                data["labels"] = [str(label.id) for label in instance.labels.all()]
+                data["labels"] = [
+                    str(label)
+                    for label in IssueLabel.objects.filter(issue=instance).values_list(
+                        "label_id", flat=True
+                    )
+                ]
 
         return data