procd: fix parsing of the has_env parameter

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

Backport of r42883

git-svn-id: svn://svn.openwrt.org/openwrt/branches/barrier_breaker@42886 3c298f89-4303-0410-b956-a3cf2f4a3e73

package/system/procd/files/nand.sh

@@ -122,7 +122,7 @@ nand_upgrade_prepare_ubi() {
 		ubiattach -m "$mtdnum"
 		sync
 		ubidev="$( nand_find_ubi "$CI_UBIPART" )"
-	 	[ -z "$has_env" ] || {
+		[ "$has_env" -gt 0 ] && {
 			ubimkvol /dev/$ubidev -n 0 -N ubootenv -s 1MiB
 			ubimkvol /dev/$ubidev -n 1 -N ubootenv2 -s 1MiB
 		}