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-bus.c b/hw/usb-bus.c
index 54027dfc41..7c823147ab 100644
--- a/hw/usb-bus.c
+++ b/hw/usb-bus.c
@@ -102,6 +102,9 @@ USBDevice *usb_create(USBBus *bus, const char *name)
 USBDevice *usb_create_simple(USBBus *bus, const char *name)
 {
     USBDevice *dev = usb_create(bus, name);
+    if (!dev) {
+        hw_error("Failed to create USB device '%s'\n", name);
+    }
     qdev_init_nofail(&dev->qdev);
     return dev;
 }