[openwrt/openwrt] mvebu: fix sysupgrade failure

[LEDE Commits]

robimarko pushed a commit to openwrt/openwrt.git, branch main:
https://git.openwrt.org/a9402a83e6cd28df2bcdd062888a16db2f4ef3e1

commit a9402a83e6cd28df2bcdd062888a16db2f4ef3e1
Author: Boris Krasnovskiy <borkra at gmail.com>
AuthorDate: Sat Oct 12 20:01:57 2024 -0400

    mvebu: fix sysupgrade failure
    
    Linksys devices do no pass $cmd at all.
    
    Fixes: #16148
    Fixes: 715634e6d144 ("base-files: upgrade: nand: use "cmd" argument for extracting command")
    Signed-off-by: Boris Krasnovskiy <borkra at gmail.com>
    Link: https://github.com/openwrt/openwrt/pull/16690
    Signed-off-by: Robert Marko <robimarko at gmail.com>
---
 package/base-files/files/lib/upgrade/nand.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/package/base-files/files/lib/upgrade/nand.sh b/package/base-files/files/lib/upgrade/nand.sh
index 9fa3cd2ddd..ca302557c8 100644
--- a/package/base-files/files/lib/upgrade/nand.sh
+++ b/package/base-files/files/lib/upgrade/nand.sh
@@ -300,7 +300,7 @@ nand_upgrade_fit() {
 # Write images in the TAR file to MTD partitions and/or UBI volumes as required
 nand_upgrade_tar() {
 	local tar_file="$1"
-	local cmd="$2"
+	local cmd="${2:-cat}"
 	local jffs2_markers="${CI_JFFS2_CLEAN_MARKERS:-0}"
 
 	# WARNING: This fails if tar contains more than one 'sysupgrade-*' directory.