No-thread: Don’t assert in ~QThreadData()

The no-thread build is not maintaining the
QThreadData refcount.

Change-Id: I80ce4151b8da9391764ed3d820943dcac0d70999
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>

src/corelib/thread/qthread.cpp

@@ -67,7 +67,9 @@ QThreadData::QThreadData(int initialRefCount)
 
 QThreadData::~QThreadData()
 {
+#if QT_CONFIG(thread)
     Q_ASSERT(_ref.loadRelaxed() == 0);
+#endif
 
     // In the odd case that Qt is running on a secondary thread, the main
     // thread instance will have been dereffed asunder because of the deref in