QupZilla, some child windows open behind the launcher/top bar

[dinamic]

ubuntu 17.04 Unity8

QupZilla, some child windows open behind the launcher/top bar
install qupzill, launch it without Xmir, from menu Edit/Preferences. it opens the preferences window behind the launcher (see screenshot)

sometimes closing the window, crashes unity8

[dinamic (dinamic6661)]

[2017-03-16:11:21:16.723] qtmir.surfaces: MirSurface[0x560fb494dd30,"qupzilla"]::updateState(hidden)
[2017-03-16:11:21:16.724] qtmir.surfaces: MirSurface[0x560fb494dd30,"qupzilla"]::setFocused(false)
[2017-03-16:11:21:16.725] qtmir.surfaces: MirSurface[0x560fb4273a60,"qupzilla"]::setFocused(true)
[2017-03-16:11:21:16.727] toplevelwindowmodel: setFocusedWindow(Window[0x560fb3ec5930, id=24, MirSurface[0x560fb4273a60,"Speed Dial - QupZilla"]])
terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<std::runtime_error> >'
  what(): Failure sending input event : Unknown channel provided
()
[2017-03-16:11:21:32.519] qtmir.screens: ScreensModel::ScreensModel