Bug 1096310 - Show message after project list load error. r=paul

browser/devtools/app-manager/app-projects.js

@@ -16,14 +16,15 @@ const { indexedDB } = require("sdk/indexed-db");
 
 const IDB = {
   _db: null,
+  databaseName: "AppProjects",
 
   open: function () {
     let deferred = promise.defer();
 
-    let request = indexedDB.open("AppProjects", 5);
+    let request = indexedDB.open(IDB.databaseName, 5);
     request.onerror = function(event) {
-      deferred.reject("Unable to open AppProjects indexedDB. " +
-                      "Error code: " + event.target.errorCode);
+      deferred.reject("Unable to open AppProjects indexedDB: " +
+                      this.error.name + " - " + this.error.message );
     };
     request.onupgradeneeded = function(event) {
       let db = event.target.result;
@@ -147,11 +148,10 @@ const store = new ObservableObject({ projects:[] });
 
 let loadDeferred = promise.defer();
 
-IDB.open().then(function (projects) {
+loadDeferred.resolve(IDB.open().then(function (projects) {
   store.object.projects = projects;
   AppProjects.emit("ready", store.object.projects);
-  loadDeferred.resolve();
-});
+}));
 
 const AppProjects = {
   load: function() {