Rotating a phone in landscape remains a black bar like the wreckage of the navigation bar

Starting an app with normal landscape mode shows the app correctly.
However, when rotating the phone up-side-down, there's a black bar that hides a part of application.
See screenshots as a reference.

Normal

Up-side-down (Black bar appears)

The problem can be easily reproduced by using empty widget app and set

android:screenOrientation="userLandscape"

in AndroidManifest.xml.

Sample code : qtbug89672.zip