Btrfs: Fix typo in extent_io.c
---

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index f13b1db..44fc94f 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -364,8 +364,7 @@
 	if (btrfs_test_opt(root, NODATASUM) ||
 	    btrfs_test_flag(inode, NODATASUM))
 		return 0;
-
-	if (state->start == start) {
+	if (state && state->start == start) {
 		private = state->private;
 		ret = 0;
 	} else {