Btrfs: fix error handling in btrfs_ioctl_send()

fget() returns NULL if error. So, we should check NULL or not.
Signed-off-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

fs/btrfs/send.c

@@ -4612,8 +4612,8 @@ long btrfs_ioctl_send(struct file *mnt_file, void __user *arg_)
 	sctx->flags = arg->flags;
 
 	sctx->send_filp = fget(arg->send_fd);
-	if (IS_ERR(sctx->send_filp)) {
-		ret = PTR_ERR(sctx->send_filp);
+	if (!sctx->send_filp) {
+		ret = -EBADF;
 		goto out;
 	}