uninitialized variable being used at _gdk_win32_surface_compute_size

Steps to reproduce

1. Invoke a surface resize on a non top level surface

Current behavior

Always resize or a exception thrown on win32

Expected outcome

Only resize when the surface size changes, and never throw an exception on win32

Version information

Gtk 4.16 from vcpkg Windows 10

Additional information

      else
        {
-          size_changed = width != impl->next_layout.configured_width ||
-                         height != impl->next_layout.configured_height;
+          size_changed = surface->width != impl->next_layout.configured_width ||
+                         surface->height != impl->next_layout.configured_height;

          surface->width = impl->next_layout.configured_width;
          surface->height = impl->next_layout.configured_height;
        }

That might work...