ensure skylink_rest is local

docker/nginx/conf.d/client.conf

@@ -176,6 +176,9 @@ server {
 			-- example response: '{"skylink":"sia://XABvi7JtJbQSMAcDwnUnmp2FKDPjg8_tTTFP4BwMSxVdEg"}'
 			local hnsres_json = json.decode(hnsres_res.body)
 
+			-- define local variable containing rest of the skylink if provided
+			local skylink_rest
+
 			if hnsres_json.skylink then
 				-- try to match the skylink with sia:// prefix
 				skylink, skylink_rest = string.match(hnsres_json.skylink, "sia://([^/?]+)(.*)")