[gnome-multi-writer] Fix a memory corruptin issue causing the UI to crash

[Richard Hughes <rhughes src gnome org>]

commit 658683caf9904b821b92dc1be133bf6c47dc04b2
Author: Richard Hughes <richard hughsie com>
Date:   Wed May 22 13:39:01 2019 +0100

    Fix a memory corruptin issue causing the UI to crash
    
    Fixes https://gitlab.gnome.org/GNOME/gnome-multi-writer/issues/8

 src/gmw-device.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/src/gmw-device.c b/src/gmw-device.c
index 0054608..bff4589 100644
--- a/src/gmw-device.c
+++ b/src/gmw-device.c
@@ -28,6 +28,7 @@
 #include "gmw-device.h"
 
 struct _GmwDevice {
+       GObject                  parent_instance;
        GError                  *error;         /* the error, if any */
        GMutex                   mutex;         /* mutex for the device */
        GmwDeviceState           state;         /* the #GmwDeviceState, e.g. %GMW_DEVICE_STATE_WRITE */