Menu shows up in Qt apps when leaving fullscreen mode

This bug happens in Xenial.
It doesn't happen in Yakkety.

How to reproduce the bug :
- Open a Qt video player (VLC or Smplayer).
- Switch the player to fullscreen mode.
- Switch back to windowed mode.

What happens :
The menu appears in the window.

What should happen :
The menu should stay hidden.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: appmenu-qt5 0.3.0+16.04.20151130-0ubuntu1
ProcVersionSignature: Ubuntu 4.4.0-53.74-generic 4.4.30
Uname: Linux 4.4.0-53-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CurrentDesktop: Unity
Date: Thu Dec 8 15:12:59 2016
InstallationDate: Installed on 2016-12-05 (2 days ago)
InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
SourcePackage: appmenu-qt5
UpgradeStatus: No upgrade log present (probably fresh install)