xwayland: Confining the cursor (cursor grab) fails if the cursor is not over the window when the grab happens

I noticed $title while testing d1x-rebirth (available in e.g. rpmfusion non-free) on a dual monitor setup.

When I move the mouse cursor to the second monitor and then start d1x-rebirth (with the controls set for using the mouse to "steer") then steering does not work until I move the mouse from the second monitor to the first one (where d1x is running fullscreen). Worse, I can also move the cursor back to the second monitor again which completely breaks the gameplay.

If I start the game with the cursor on the first monitor then everything is fine.