odhcp6c: fix appending of emtpy sendopt value (FS#1336)

Don't append an empty sendopts value as odhcp6c bails out
immediately on an empty -x option triggering an infinite start
loop of odhcp6c

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>

package/network/ipv6/odhcp6c/Makefile

@@ -8,7 +8,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=odhcp6c
-PKG_RELEASE:=7
+PKG_RELEASE:=8
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL=$(PROJECT_GIT)/project/odhcp6c.git

package/network/ipv6/odhcp6c/files/dhcpv6.sh

@@ -77,7 +77,7 @@ proto_dhcpv6_setup() {
 
 	sendopts_cb() {
 		local val="$1"
-		append opts "-x$val"
+		[ -n "$val" ] && append opts "-x$val"
 	}
 
 	json_for_each_item sendopts_cb sendopts