fix background refresh being broken when no counter data is sent

functions.js

@@ -562,11 +562,13 @@ function parse_counters_reply(transport, scheduled_call) {
 
 	var counters = reply.getElementsByTagName("counters")[0];
 	
-	parse_counters(counters, scheduled_call);
+	if (counters)
+		parse_counters(counters, scheduled_call);
 
 	var runtime_info = reply.getElementsByTagName("runtime-info")[0];
 
-	parse_runtime_info(runtime_info);
+	if (runtime_info)
+		parse_runtime_info(runtime_info);
 
 	if (feedsSortByUnread()) {
 		resort_feedlist();

modules/backend-rpc.php

@@ -293,15 +293,13 @@
 
 			print "<rpc-reply>";
 
-			print "<counters><![CDATA[";
-
 			if ($global_unread_caller != $global_unread) {
+				print "<counters><![CDATA[";
 				$omode = $_REQUEST["omode"];
 				print json_encode(getAllCounters($link, $omode));
+				print "]]></counters>";
 			}
  
-			print "]]></counters>";
-
 			print_runtime_info($link);
 
 			print "</rpc-reply>";