procd: allow adding empty strings to arrays

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

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@42456 3c298f89-4303-0410-b956-a3cf2f4a3e73

package/system/procd/files/procd.sh

@@ -75,7 +75,7 @@ _procd_close_service() {
 }
 
 _procd_add_array_data() {
-	while [ -n "$1" ]; do
+	while [ "$#" -gt 0 ]; do
 		json_add_string "" "$1"
 		shift
 	done