fix json handling

import_api_app/resources/WriteJobResultsToDrupal.py

@@ -129,13 +129,13 @@ def write_results(job_drupal_uuid, job_log_drupal_uuid, status, report):
         raise ImportApiError(message)
     if previous_status == 'FAILED':
         status = previous_status
-    if previous_report is None:
+    if previous_report is None or previous_report == 'null':
         previous_report_json = {}
     else:
         previous_report_json = json.loads(previous_report)
     step = report['step']
     previous_report_json[step] = report
-    reportString = json.dumps(previous_report)
+    reportString = json.dumps(previous_report_json)
 
     # update values in drupal:
     patchCalls = {}