finished fixing job through workflow node

related to #4182

awx/api/serializers.py

@@ -607,7 +607,11 @@ class UnifiedJobSerializer(BaseSerializer):
         summary_fields = super(UnifiedJobSerializer, self).get_summary_fields(obj)
         if obj.spawned_by_workflow:
             summary_fields['source_workflow_job'] = {}
+            try:
                 summary_obj = obj.unified_job_node.workflow_job
+            except ObjectDoesNotExist:
+                return summary_fields
+
             for field in SUMMARIZABLE_FK_FIELDS['job']:
                 val = getattr(summary_obj, field, None)
                 if val is not None:

awx/main/models/unified_jobs.py

@@ -20,6 +20,7 @@ from django.utils.translation import ugettext_lazy as _
 from django.utils.timezone import now
 from django.utils.encoding import smart_text
 from django.apps import apps
+from django.core.exceptions import ObjectDoesNotExist
 
 # Django-Polymorphic
 from polymorphic import PolymorphicModel
@@ -780,13 +781,19 @@ class UnifiedJob(PolymorphicModel, PasswordFieldsModel, CommonModelNameNotUnique
     @property
     def workflow_job_id(self):
         if self.spawned_by_workflow:
+            try:
                 return self.unified_job_node.workflow_job.pk
+            except ObjectDoesNotExist:
+                pass
         return None
 
     @property
     def workflow_node_id(self):
         if self.spawned_by_workflow:
+            try:
                 return self.unified_job_node.pk
+            except ObjectDoesNotExist:
+                pass
         return None
 
     @property