With libusb-compat, usb_open() calls must be checked for their return value, as
NULL is now returned on failure.

Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>

diff -Nuar pilot-link-0.12.3.orig/libpisock/libusb.c pilot-link-0.12.3/libpisock/libusb.c
--- pilot-link-0.12.3.orig/libpisock/libusb.c	2007-02-09 08:06:22.000000000 -0800
+++ pilot-link-0.12.3/libpisock/libusb.c	2009-05-18 17:32:16.316895284 -0700
@@ -141,6 +141,12 @@
 
 			LOG((PI_DBG_DEV, PI_DBG_LVL_DEBUG, "%s: USB_handle=%p\n", 
 				__FILE__, USB_handle));
+			
+			if(USB_handle == NULL) {
+			    LOG((PI_DBG_DEV, PI_DBG_LVL_DEBUG, "%s: Unable to open device.\n",
+					__FILE__));
+			    continue;
+			}
 
 			data->ref = USB_handle;