3bc3740a9e
The NULL check was inverted, meaning we'd grab with no leader device.
That meant updates coming from the what-should-have-been leader device
getting lost because incorrectly being classified as non-leader of
the grab.
Fix this by only allowing to grab if we have a device, and always mark
the current tool device as the grab leader.
Fixes: e4004a7c4f ("wayland: Use the tool's current_tablet device instead of caching it")
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/4033>