Fix for assertion failure

Change-Id: I97b9ecc37e938a3050793fc746288243a1cb40b7
Reviewed-by: Peter Hartmann <peter.hartmann@nokia.com>

src/network/access/qnetworkaccessauthenticationmanager.cpp

@@ -159,6 +159,11 @@ void QNetworkAccessAuthenticationManager::cacheProxyCredentials(const QNetworkPr
     QString realm = authenticator->realm();
     QNetworkProxy proxy = p;
     proxy.setUser(authenticator->user());
+
+    // don't cache null passwords, empty password may be valid though
+    if (authenticator->password().isNull())
+        return;
+
     // Set two credentials: one with the username and one without
     do {
         // Set two credentials actually: one with and one without the realm

src/network/access/qnetworkaccessauthenticationmanager_p.h

@@ -73,7 +73,7 @@ public:
     QString user;
     QString password;
     bool isNull() {
-        return domain.isNull();
+        return domain.isNull() && user.isNull() && password.isNull();
     }
 };
 Q_DECLARE_TYPEINFO(QNetworkAuthenticationCredential, Q_MOVABLE_TYPE);