memory leak of QFontEngineData object

QFont::cleanup(); and cleanupThreadData(); in QGuiApplicationPrivate::~QGuiApplicationPrivate() will trigger QFontCache::~QFontCache() function being called and at that time the platform_theme object still hold some fonts object, This will cause the QFontEngineData object hold by those fonts can never been deleted.
I have submit a change (https://codereview.qt-project.org/#change,23253) to fix this leak, but that change has been reverted (https://codereview.qt-project.org/#change,23615) due to the reason "The fix causes crashes on exit in Qt Declarative.". But I can not produce this crash on Windows 7, so the only thing I can do is to submit a bug report.