Assertion failure in QCoreApplication::sendEvent if a child object of a parent object moved to different thread is destroyed in the parent destructor

First reported in QTBUG-20816 but this appears to have been closed without due consideration. 20816 has a very explicit description.

I'm seeing the same bug in Qt 5.8.0 but only on Windows (MSVC2013). The code compiled in 5.9.3 on macOS High Sierra does not trigger the ASSERT.

I have verified that the both the parent QObject and the dynamically allocated child QObject have the same thread, just before destroying the child in the parent destructor. If I explicitly destroy the child, the ASSERT triggers. If I don't destroy the child, the parent destructor proceeds fine.