Bug 1261311 - Fix storage inspector promise rejections r=mratcliffe

Hide the errors for now.

MozReview-Commit-ID: Fj1wYvZ4UFx

devtools/client/storage/ui.js

@@ -170,6 +170,8 @@ StorageUI.prototype = {
     if (typeof actor.getEditableFields !== "undefined") {
       actor.getEditableFields().then(fields => {
         this.table.makeFieldsEditable(fields);
+      }).then(() => {
+        // Do nothing
       });
     } else if (this.table._editableFieldsEngine) {
       this.table._editableFieldsEngine.destroy();