hdw->cmd_debug_state = 1;
-       if (write_len) {
+       if (write_len && write_data)
                hdw->cmd_debug_code = ((unsigned char *)write_data)[0];
-       } else {
+       else
                hdw->cmd_debug_code = 0;
-       }
        hdw->cmd_debug_write_len = write_len;
        hdw->cmd_debug_read_len = read_len;
 
        setup_timer(&timer, pvr2_ctl_timeout, (unsigned long)hdw);
        timer.expires = jiffies + timeout;
 
-       if (write_len) {
+       if (write_len && write_data) {
                hdw->cmd_debug_state = 2;
                /* Transfer write data to internal buffer */
                for (idx = 0; idx < write_len; idx++) {
                        goto done;
                }
        }
-       if (read_len) {
+       if (read_len && read_data) {
                /* Validate results of read request */
                if ((hdw->ctl_read_urb->status != 0) &&
                    (hdw->ctl_read_urb->status != -ENOENT) &&