Xwayland with linux_dmabuf v4 feedback support is broken on `WLR_RENDERER=vulkan`

With WLR_RENDERER=vulkan and Xwayland with xorg/xserver!818 (merged), Xwayland apps can't render anything.

Environment: Arch Linux with wlroots 0.16.1 and sway 1.8, Xwayland xorg/xserver@d67383a6.

Can also reproduce on latest master of wlroots and sway, can't reproduce on xorg/xserver@16e7cdba.

Edited Jan 21, 2023 by q234rty

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