Window doesn't set proper size during initialization on Wayland

[MiKom]

Steps to reproduce

Run the gui_window_example on Wayland

Expected result

Window shows up with size 800x600 because that's the default size in window.h

Actual result

Window has size 0x0.

Notes

That because during window creation neither LinuxWaylandPlatformWindow::create nor LinuxWaylandPlatformWindow::map does any resizing and we get a 0x0 surface.