do not set undefined properties

src/services/cryptoService.js

@@ -51,6 +51,11 @@ function initCryptoService(constantsService) {
     CryptoService.prototype.setEncKey = function (encKey) {
         var deferred = Q.defer();
 
+        if (encKey === undefined) {
+            deferred.resolve();
+            return deferred.promise;
+        }
+
         chrome.storage.local.set({
             'encKey': encKey
         }, function () {
@@ -64,6 +69,11 @@ function initCryptoService(constantsService) {
     CryptoService.prototype.setEncPrivateKey = function (encPrivateKey) {
         var deferred = Q.defer();
 
+        if (encPrivateKey === undefined) {
+            deferred.resolve();
+            return deferred.promise;
+        }
+
         chrome.storage.local.set({
             'encPrivateKey': encPrivateKey
         }, function () {

src/services/syncService.js

@@ -87,7 +87,7 @@ function initSyncService() {
 
         self.apiService.getProfile(function (response) {
             self.userService.getSecurityStamp().then(function (stamp) {
-                if (stamp && stamp != response.securityStamp) {
+                if (stamp && stamp !== response.securityStamp) {
                     if (self.logoutCallback) {
                         self.logoutCallback(true, function () { });
                     }

src/services/userService.js

@@ -38,6 +38,11 @@ function initUserService() {
     UserService.prototype.setSecurityStamp = function (stamp) {
         var deferred = Q.defer();
 
+        if (stamp === undefined) {
+            deferred.resolve();
+            return deferred.promise;
+        }
+
         _stamp = stamp;
         var stampObj = {};
         stampObj[stampKey] = stamp;