[Android] Crash at QQuickWindowPrivate::flushFrameSynchronousEvents()

Starting with Qt 5.9, I have begun receiving reports through the ANRs & crashes section of the Google Play Console about this crash. This happens to all the apps that I have updated to 5.9 and 5.9.1. The Android build SDK I used is android-16. I did not have these problems before. This is a regression.

2 minutes ago on app version 216273
Samsung Galaxy S7 (herolte), 4096MB RAM, Android 7.0
Report 1 of 2,172

backtrace:
  native: pc 00000000000af2e2  /data/app/com.gsoftteam.connectbubbles-1/lib/arm/libQt5Quick.so
  native: pc 0000000000119463  /data/app/com.gsoftteam.connectbubbles-1/lib/arm/libQt5Quick.so (_ZN19QQuickWindowPrivate27flushFrameSynchronousEventsEv+50)

These reports are numerous and seem to be affecting high-end devices (S6, S7, S6 Edge, S7 Edge and many others). Unfortunately I haven't been able to replicate a crash on a device of my own. Thus I am unable to provide more details about this issue.

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But because of these crashes, all Qt 5.9+ apps might be downranked: https://android-developers.googleblog.com/2017/08/how-were-helping-people-find-quality.html . Apps with crashes are now penalized.