If no valid CHID value has previously been set on an HWA, writing a
value of all zeros will cause a kernel panic in uwb_radio_stop because
wusbhc->uwb_rc has not been set.  This patch skips the call to
uwb_radio_stop if wusbhc->uwb_rc has not been initialized.
Signed-off-by: Thomas Pugliese <thomas.pugliese@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 
        if (chid)
                result = uwb_radio_start(&wusbhc->pal);
-       else
+       else if (wusbhc->uwb_rc)
                uwb_radio_stop(&wusbhc->pal);
 
        return result;