Mark Finding properties related_fields, jira_creation and jira_change as nullable (#10371)

Co-authored-by: Camilo Cota <ccota@redhat.com>

Author: ccronca

dojo/api_v2/serializers.py

@@ -1645,10 +1645,10 @@ class FindingSerializer(TaggitSerializer, serializers.ModelSerializer):
     age = serializers.IntegerField(read_only=True)
     sla_days_remaining = serializers.IntegerField(read_only=True)
     finding_meta = FindingMetaSerializer(read_only=True, many=True)
-    related_fields = serializers.SerializerMethodField()
+    related_fields = serializers.SerializerMethodField(allow_null=True)
     # for backwards compatibility
-    jira_creation = serializers.SerializerMethodField(read_only=True)
-    jira_change = serializers.SerializerMethodField(read_only=True)
+    jira_creation = serializers.SerializerMethodField(read_only=True, allow_null=True)
+    jira_change = serializers.SerializerMethodField(read_only=True, allow_null=True)
     display_status = serializers.SerializerMethodField()
     finding_groups = FindingGroupSerializer(
         source="finding_group_set", many=True, read_only=True