gnome-shell doesn't start on Xorg anymore (but mutter does)

As of today, gnome-shell doesn't start on Xorg anymore (but mutter does)...

Clutter:ERROR:../clutter/clutter/clutter-actor.c:16056:clutter_actor_get_real_resource_scale: assertion failed: (guessed_scale >= 1.f)
Bail out! Clutter:ERROR:../clutter/clutter/clutter-actor.c:16056:clutter_actor_get_real_resource_scale: assertion failed: (guessed_scale >= 1.f)
== Stack trace for context 0x5581a31303e0 ==
#0   5581a3596a60 i   resource:///org/gnome/shell/ui/popupMenu.js:275 (2de69dd18718 @ 58)
#1   5581a3596990 i   resource:///org/gnome/shell/ui/popupMenu.js:534 (2de69dd192e0 @ 84)
#2   5581a35968c0 i   resource:///org/gnome/shell/ui/popupMenu.js:545 (2de69dd193d0 @ 32)
#3   5581a3596808 i   resource:///org/gnome/shell/ui/backgroundMenu.js:14 (2de69dd05e98 @ 83)
#4   5581a3596768 i   resource:///org/gnome/shell/ui/backgroundMenu.js:28 (2de69dd05bc8 @ 46)
#5   5581a35966c8 i   resource:///org/gnome/shell/ui/layout.js:444 (28fd802f29e8 @ 30)
#6   5581a3596610 i   resource:///org/gnome/shell/ui/layout.js:453 (28fd802f2a60 @ 129)
#7   5581a3596568 i   resource:///org/gnome/shell/ui/layout.js:483 (28fd802f2b50 @ 199)
#8   5581a35964d0 i   resource:///org/gnome/shell/ui/layout.js:543 (28fd802f2e20 @ 62)
#9   5581a35963f8 i   resource:///org/gnome/shell/ui/layout.js:297 (28fd802f25b0 @ 1564)
#10   5581a3596358 i   resource:///org/gnome/shell/ui/main.js:195 (28fd802cbc40 @ 132)
#11   5581a35962a8 i   resource:///org/gnome/shell/ui/main.js:161 (28fd802cba60 @ 324)
#12   5581a3596220 i   <main>:1 (28fd8028d178 @ 48)