dm-crypt fix for zero-length key.

Signed-Off-By: Alasdair G Kergon <agk@redhat.com>
--- diff/drivers/md/dm-crypt.c	2004-11-10 15:05:04.000000000 +0000
+++ source/drivers/md/dm-crypt.c	2004-11-10 15:05:24.000000000 +0000
@@ -569,8 +569,8 @@
 	}
 
 	cc->key_size = key_size;
-	if ((key_size == 0 && strcmp(argv[1], "-") != 0)
-	    || crypt_decode_key(cc->key, argv[1], key_size) < 0) {
+	if ((!key_size && strcmp(argv[1], "-") != 0) ||
+	    (key_size && crypt_decode_key(cc->key, argv[1], key_size) < 0)) {
 		ti->error = PFX "Error decoding key";
 		goto bad1;
 	}