A client can create a token without any seat, serial, or surface. In
this case, we'd still try to grab, which would run into some unforseen
code paths, potentially resulting in the following crash:
0) meta_wayland_tablet_seat_device_added (tablet_seat=0x55dff4271c90,
device=0x7f87b80655b0) at
../src/wayland/meta-wayland-tablet-seat.c:200
1) meta_wayland_tablet_seat_new (seat=0x0, manager=0x55dff3ec7b40) at
../src/wayland/meta-wayland-tablet-seat.c:283
2) meta_wayland_tablet_manager_ensure_seat (manager=manager@entry=0x55dff3ec7b40,
seat=seat@entry=0x0) at
../src/wayland/meta-wayland-tablet-manager.c:239
3) meta_wayland_tablet_manager_ensure_seat (seat=0x0, manager=0x55dff3ec7b40) at
../src/wayland/meta-wayland-touch.c:595
4) meta_wayland_seat_get_grab_info (seat=0x0, surface=0x55dff43ff5b0,
serial=0, require_pressed=0, x=0x0, y=0x0) at
../src/wayland/meta-wayland-seat.c:479
5) activation_activate (...) at
../src/wayland/meta-wayland-activation.c:261
Fix this by not trying to grab if not enough parameters was passed when
creating the token. Also add a test case that reproduces the above
crash.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2081>
