[mutter/gnome-3-26] clutter/evdev: Ignore unknown touch points

[Jonas Ådahl <jadahl src gnome org>]

commit 97f099d8cec1628c42a76beee672661286b74d08
Author: Jonas Ådahl <jadahl gmail com>
Date:   Mon Dec 11 18:22:21 2017 +0800

    clutter/evdev: Ignore unknown touch points
    
    We might receive touch events for unknown touch points, for example
    when starting mutter while touching the screen (resulting in no
    touch-down event ever being received). Avoid crashing when this happens
    by just dropping these events on the floor.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=791371

 .../clutter/evdev/clutter-device-manager-evdev.c   |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)
---
diff --git a/clutter/clutter/evdev/clutter-device-manager-evdev.c 
b/clutter/clutter/evdev/clutter-device-manager-evdev.c
index f40746a..f9a3a14 100644
--- a/clutter/clutter/evdev/clutter-device-manager-evdev.c
+++ b/clutter/clutter/evdev/clutter-device-manager-evdev.c
@@ -1459,6 +1459,8 @@ process_device_event (ClutterDeviceManagerEvdev *manager_evdev,
         slot = libinput_event_touch_get_slot (touch_event);
         time_us = libinput_event_touch_get_time_usec (touch_event);
         touch_state = clutter_seat_evdev_get_touch (seat, slot);
+        if (!touch_state)
+          break;
 
         notify_touch_event (device, CLUTTER_TOUCH_END, time_us, slot,
                            touch_state->coords.x, touch_state->coords.y);
@@ -1497,6 +1499,9 @@ process_device_event (ClutterDeviceManagerEvdev *manager_evdev,
                                                     stage_height);
 
         touch_state = clutter_seat_evdev_get_touch (seat, slot);
+        if (!touch_state)
+          break;
+
         touch_state->coords.x = x;
         touch_state->coords.y = y;