Cannot unregister QGestureRecognizer without access violation

When unregistering Qt-GestureRecognizers, e.g. with

QGestureRecognizer::unregisterRecognizer(Qt::PanGesture);

the recognizers are not completely released. They are just moved to 
m_deletedRecognizers/m_obsoleteGestures. Thus is not a problem - yet. Probably the bug could be there.

After this, destroying the QApplication (and implicitly the QGestureManager), it causes them to
delete the object of recognizers _before_ it can be delete the obsolete ones.

See qgesturemanager.cpp:

QGestureManager::~QGestureManager()
{
  qDeleteAll(m_recognizers);
  // ^--^ implies deleting the Keys used in m_obsoleteGestures.

  foreach (QGestureRecognizer *recognizer, m_obsoleteGestures.keys()) {
     // does not crash, but the value is no longer valid        
     qDeleteAll(m_obsoleteGestures.value(recognizer)); 

     delete recognizer; // Access violation now
  }
  m_obsoleteGestures.clear();
}

Where is the error?

Problem should be reproducible with the smallest Qt-Example and did not appear in Qt 5.9.