crash in xwl_pointer_warp_emulator_maybe_lock

[Christian Rauch]

I got a nonreproducible crash of Xwayland with the following backtrace:

```
#0 __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
#1 0x00007f88c73c4859 in __GI_abort () at abort.c:79
#2 0x000055dfca054e40 in OsAbort () at ../../../../os/utils.c:1351
#3 0x000055dfca05a279 in AbortServer () at ../../../../os/log.c:879
#4 0x000055dfca05b0da in FatalError (f=f@entry=0x55dfca080d90 "Caught signal %d (%s). Server aborting\n") at ../../../../os/log.c:1017
#5 0x000055dfca052189 in OsSigHandler (unused=<optimized out>, sip=0x7ffc013b4070, signo=11) at ../../../../os/osinit.c:156
#6 OsSigHandler (signo=11, sip=0x7ffc013b4070, unused=<optimized out>) at ../../../../os/osinit.c:110
#7 <signal handler called>
#8 0x000055dfc9ef041e in xwl_pointer_warp_emulator_maybe_lock (warp_emulator=warp_emulator@entry=0x55dfccbf5ce0, xwl_window=<optimized out>, sprite=<optimized out>, x=x@entry=683,
    y=y@entry=384) at ../../../../../hw/xwayland/xwayland-input.c:2694
#9 0x000055dfc9ef3fa1 in xwl_pointer_warp_emulator_warp (y=384, x=683, sprite=<optimized out>, xwl_window=<optimized out>, warp_emulator=0x55dfccbf5ce0)
    at ../../../../../hw/xwayland/xwayland-input.c:2823
#10 xwl_seat_emulate_pointer_warp (xwl_seat=<optimized out>, xwl_window=<optimized out>, sprite=<optimized out>, x=683, y=384) at ../../../../../hw/xwayland/xwayland-input.c:2823
#11 0x000055dfca028da2 in ProcWarpPointer (client=0x55dfcc3e2fc0) at ../../../../dix/events.c:3624
#12 0x000055dfca01b564 in Dispatch () at ../../../../dix/dispatch.c:478
#13 0x000055dfca01f614 in dix_main (argc=16, argv=0x7ffc013b4788, envp=<optimized out>) at ../../../../dix/main.c:276
#14 0x00007f88c73c60b3 in __libc_start_main (main=0x55dfc9eed580 <main>, argc=16, argv=0x7ffc013b4788, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>,
    stack_end=0x7ffc013b4778) at ../csu/libc-start.c:308
#15 0x000055dfc9eed5be in _start ()
```

The issue has been reported upstream as: https://gitlab.freedesktop.org/xorg/xserver/-/issues/1169

I am also attaching my apport crash file "_usr_bin_Xwayland.1000.crash" as I cannot see if this has been reported already by apport. I don't see it in the list of my own crash reports as described in https://popey.com/blog/2021/03/finding-ubuntu-crash-reports/.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: xwayland 2:1.20.9-2ubuntu1.2~20.04.2
ProcVersionSignature: Ubuntu 5.8.0-50.56~20.04.1-generic 5.8.18
Uname: Linux 5.8.0-50-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.16
Architecture: amd64
BootLog: Error: [Errno 13] Keine Berechtigung: '/var/log/boot.log'
CasperMD5CheckResult: skip
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: None
CurrentDesktop: ubuntu:GNOME
Date: Sun Apr 25 13:27:10 2021
DistUpgraded: Fresh install
DistroCodename: focal
DistroVariant: ubuntu
ExtraDebuggingInterest: Yes
GraphicsCard:
 Intel Corporation HD Graphics 5500 [8086:1616] (rev 09) (prog-if 00 [VGA controller])
   Subsystem: Lenovo HD Graphics 5500 [17aa:5034]
MachineType: LENOVO 20BUS15H00
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-5.8.0-50-generic root=UUID=d1694733-96aa-4a12-9c6f-2ed18308ab56 ro quiet splash vt.handoff=7
SourcePackage: xorg-server
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 08/14/2019
dmi.bios.release: 1.37
dmi.bios.vendor: LENOVO
dmi.bios.version: JBET73WW (1.37 )
dmi.board.asset.tag: Not Available
dmi.board.name: 20BUS15H00
dmi.board.vendor: LENOVO
dmi.board.version: SDK0E50510 WIN
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: None
dmi.ec.firmware.release: 1.4
dmi.modalias: dmi:bvnLENOVO:bvrJBET73WW(1.37):bd08/14/2019:br1.37:efr1.4:svnLENOVO:pn20BUS15H00:pvrThinkPadT450:rvnLENOVO:rn20BUS15H00:rvrSDK0E50510WIN:cvnLENOVO:ct10:cvrNone:
dmi.product.family: ThinkPad T450
dmi.product.name: 20BUS15H00
dmi.product.sku: LENOVO_MT_20BU_BU_Think_FM_ThinkPad T450
dmi.product.version: ThinkPad T450
dmi.sys.vendor: LENOVO
version.compiz: compiz N/A
version.libdrm2: libdrm2 2.4.102-1ubuntu1~20.04.1
version.libgl1-mesa-dri: libgl1-mesa-dri 20.2.6-0ubuntu0.20.04.1
version.libgl1-mesa-glx: libgl1-mesa-glx 20.2.6-0ubuntu0.20.04.1
version.xserver-xorg-core: xserver-xorg-core 2:1.20.9-2ubuntu1.2~20.04.2
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:19.1.0-1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20200226-1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.16-1