On some occasion QScreen::devicePixelRatio() crashes.

``` 
0 Qt5Gui.dll!QScreen::devicePixelRatio() [qscreen.cpp : 292 + 0x0] 
1 Qt5WebEngineCore.dll!QtWebEngineCore::GetScreenInfoFromNativeWindow(QWindow *,blink::WebScreenInfo *) [chromium_overrides.cpp : 71 + 0x6] 
2 Qt5WebEngineCore.dll!QtWebEngineCore::RenderWidgetHostViewQt::GetScreenInfo(blink::WebScreenInfo *) [render_widget_host_view_qt.cpp : 712 + 0xb] 
3 Qt5WebEngineCore.dll!content::RenderWidgetHostImpl::GetWebScreenInfo(blink::WebScreenInfo *) [render_widget_host_impl.cc : 1132 + 0x10] 
4 Qt5WebEngineCore.dll!content::RenderWidgetHostImpl::GetResizeParams(ViewMsg_Resize_Params *) [render_widget_host_impl.cc : 581 + 0x14] 
5 Qt5WebEngineCore.dll!content::RenderWidgetHostImpl::WasResized() [render_widget_host_impl.cc : 640 + 0x8] 
6 Qt5WebEngineCore.dll!content::RenderViewHostImpl::OnRenderViewReady() [render_view_host_impl.cc : 1029 + 0x10] 
7 Qt5WebEngineCore.dll!IPC::Message::Dispatch<content::ChildThreadImpl,content::ChildThreadImpl,void>(IPC::Message const *,content::ChildThreadImpl *,content::ChildThreadImpl *,void *,void ( content::ChildThreadImpl::*)(void)) [ipc_message.h : 148 + 0x17] 
8 Qt5WebEngineCore.dll!content::RenderViewHostImpl::OnMessageReceived(IPC::Message const &) [render_view_host_impl.cc : 903 + 0x4b] 
9 Qt5WebEngineCore.dll!content::RenderProcessHostImpl::OnMessageReceived(IPC::Message const &) [render_process_host_impl.cc : 1569 + 0x7] 
... (truncated)