Fix -usbdevice crash

If -usbdevice is used on a machine with no USB busses, usb_create
will fail and return NULL.  Patch below handles this failure gracefully
rather than crashing when we try to init the device.

Signed-off-by: Paul Brook <paul@codesourcery.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/hw/usb-msd.c b/hw/usb-msd.c
index 36991f8833..1a11bc557e 100644
--- a/hw/usb-msd.c
+++ b/hw/usb-msd.c
@@ -592,6 +592,9 @@ static USBDevice *usb_msd_init(const char *filename)
 
     /* create guest device */
     dev = usb_create(NULL /* FIXME */, "usb-storage");
+    if (!dev) {
+        return NULL;
+    }
     qdev_prop_set_drive(&dev->qdev, "drive", dinfo);
     if (qdev_init(&dev->qdev) < 0)
         return NULL;