[mutter/gnome-3-36] backends: Ensure to clear the last updated device on device removal

[Jonas Ådahl <jadahl src gnome org>]

commit e147c3feaf7fbffa5785dd768aa96d9133ba66c8
Author: Carlos Garnacho <carlosg gnome org>
Date:   Fri Sep 25 18:51:37 2020 +0200

    backends: Ensure to clear the last updated device on device removal
    
    If the last updated device is removed, ensure that it does result in
    a ::last-device-changed with a NULL device.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1460
    (cherry picked from commit 089be8b71dd163fa9a8c38b985cb150fad8152c5)

 src/backends/meta-backend.c | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/src/backends/meta-backend.c b/src/backends/meta-backend.c
index 0a0b9d778d..b1c6aa86cc 100644
--- a/src/backends/meta-backend.c
+++ b/src/backends/meta-backend.c
@@ -471,6 +471,9 @@ on_device_removed (ClutterSeat        *seat,
                                                    !has_touchscreen);
         }
     }
+
+  if (priv->current_device == device)
+    meta_backend_update_last_device (backend, NULL);
 }
 
 static void