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-serial.c b/hw/usb-serial.c
index c3f3401370..1410b11b2b 100644
--- a/hw/usb-serial.c
+++ b/hw/usb-serial.c
@@ -594,6 +594,9 @@ static USBDevice *usb_serial_init(const char *filename)
         return NULL;
 
     dev = usb_create(NULL /* FIXME */, "usb-serial");
+    if (!dev) {
+        return NULL;
+    }
     qdev_prop_set_chr(&dev->qdev, "chardev", cdrv);
     if (vendorid)
         qdev_prop_set_uint16(&dev->qdev, "vendorid", vendorid);