refactor(travisService/test): added null check to response body

 refactor(travisService/test):  response body could be null for eg when a json converter is unable to convert non-json format

igor-monitor-travis/src/main/java/com/netflix/spinnaker/igor/travis/service/TravisService.java

@@ -448,7 +448,7 @@ private Optional<String> getAndCacheJobLog(int jobId) {
       if (e instanceof SpinnakerHttpException) { // only SpinnakerHttpException has a response body
         try {
           Map<String, Object> body = ((SpinnakerHttpException) e).getResponseBody();
-          if ("log_expired".equals(body.get("error_type"))) {
+          if (body != null && "log_expired".equals(body.get("error_type"))) {
             log.info(
                 "{}: The log for job id {} has expired and the corresponding build was ignored",
                 groupKey,