[users] Protect against JobQueue or GS being NULL

- Avoid SIGSEGV in tests, make sure JobQueue exists, GS optional

src/modules/users/Config.cpp

@@ -34,6 +34,11 @@ static void
 updateGSAutoLogin( bool doAutoLogin, const QString& login )
 {
     Calamares::GlobalStorage* gs = Calamares::JobQueue::instance()->globalStorage();
+    if ( !gs )
+    {
+        cWarning() << "No Global Storage available";
+        return;
+    }
 
     if ( doAutoLogin && !login.isEmpty() )
     {

src/modules/users/Tests.cpp

@@ -53,6 +53,11 @@ UserTests::initTestCase()
 {
     Logger::setupLogLevel( Logger::LOGDEBUG );
     cDebug() << "Users test started.";
+
+    if ( !Calamares::JobQueue::instance() )
+    {
+        (void)new Calamares::JobQueue();
+    }
 }
 
 void