usb-mtp: print parent path in IN_IGNORED trace fn

Fix a possible null dereference when deleting a folder and
its contents. An ignored event might be received for its contents
after the parent folder is deleted which will return a null object.
Signed-off-by: NBandan Das <bsd@redhat.com>
Message-id: 20180223164829.29683-3-bsd@redhat.com
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

hw/usb/dev-mtp.c

@@ -540,9 +540,8 @@ static void inotify_watchfn(void *arg)
                 break;
 
             case IN_IGNORED:
-                o = usb_mtp_object_lookup_name(parent, event->name, event->len);
-                trace_usb_mtp_inotify_event(s->dev.addr, o->path,
-                                      event->mask, "Obj ignored");
+                trace_usb_mtp_inotify_event(s->dev.addr, parent->path,
+                                      event->mask, "Obj parent dir ignored");
                 break;
 
             default: