Sheriff-o-matic: Fix inverted condition when persisting annotations

Tools/GardeningServer/model/ct-failure-group.html

 <!--
 Copyright 2014 The Chromium Authors. All rights reserved.
 Use of this source code is governed by a BSD-style license that can be
 found in the LICENSE file.
 -->
 
 <script>
 function CTFailureGroup(key, failures, annotation) {
   this.key = key;
   this.failures = failures;
@@ skipping 24 matching lines @@
 
     Object.keys(newAnnotation, function(key, value) {
       if (value === 'undefined') {
         delete annotation[key];
       } else {
         annotation[key] = value;
       }
     });
 
     if (Object.size(annotation) == 0) {
+      delete annotations[this.key];
+    } else {
       annotations[this.key] = annotation;
-    } else {
-      delete annotations[this.key];
     }
 
     localStorage.CTFailureGroupAnnotations = JSON.stringify(annotations);
 
     this.annotation = annotation;
     this._computeProperties();
   }.bind(this));
 };
 
 CTFailureGroup.fetchAnnotations = function() {
   // FIXME: Fetch annotations from frontend.
   var stored = localStorage.CTFailureGroupAnnotations;
   var annotations = stored ? JSON.parse(stored) : {};
   return Promise.resolve(annotations);
 };
 </script>