[SCSI] iscsi_boot_sysfs: have this module check for null on destruction

This moves the check for NULL boot_sets to the iscsi_boot_sysfs
module instead of having the drivers do it.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
diff --git a/drivers/scsi/iscsi_boot_sysfs.c b/drivers/scsi/iscsi_boot_sysfs.c
index df6bff7..4274ce9 100644
--- a/drivers/scsi/iscsi_boot_sysfs.c
+++ b/drivers/scsi/iscsi_boot_sysfs.c
@@ -472,6 +472,9 @@
 {
 	struct iscsi_boot_kobj *boot_kobj, *tmp_kobj;
 
+	if (!boot_kset)
+		return;
+
 	list_for_each_entry_safe(boot_kobj, tmp_kobj,
 				 &boot_kset->kobj_list, list)
 		iscsi_boot_remove_kobj(boot_kobj);