volume_id: abort early on read failures.
 should help with probing missing fdd's

diff --git a/util-linux/volume_id/udf.c b/util-linux/volume_id/udf.c
index 55e97a7..e272e19 100644
--- a/util-linux/volume_id/udf.c
+++ b/util-linux/volume_id/udf.c
@@ -55,8 +55,9 @@
 
 #define UDF_VSD_OFFSET			0x8000
 
-int volume_id_probe_udf(struct volume_id *id, uint64_t off)
+int volume_id_probe_udf(struct volume_id *id /*,uint64_t off*/)
 {
+#define off ((uint64_t)0)
 	struct volume_descriptor *vd;
 	struct volume_structure_descriptor *vsd;
 	unsigned bs;