Make locktimer more robust

If no HTML element with the id wiki__text exists, locktimer.init led to a
JavaScript error.

lib/exe/js.php

@@ -113,7 +113,7 @@ function js_out(){
     js_runonstart("initSizeCtl('size__ctl','wiki__text')");
     js_runonstart("initToolbar('tool__bar','wiki__text',toolbar)");
     if($conf['locktime'] != 0){
-        js_runonstart("locktimer.init(".($conf['locktime'] - 60).",'".js_escape($lang['willexpire'])."',".$conf['usedraft'].")");
+        js_runonstart("locktimer.init(".($conf['locktime'] - 60).",'".js_escape($lang['willexpire'])."',".$conf['usedraft'].", 'wiki__text')");
     }
     js_runonstart('scrollToMarker()');
     js_runonstart('focusMarker()');

lib/scripts/locktimer.js

@@ -9,7 +9,11 @@ var locktimer = {
     msg:      '',
     pageid:   '',
 
-    init: function(timeout,msg,draft){
+    init: function(timeout,msg,draft,edid){
+        var edit = $(edid);
+        if(!edit) return;
+        if(edit.readOnly) return;
+
         // init values
         locktimer.timeout  = timeout*1000;
         locktimer.msg      = msg;
@@ -19,7 +23,6 @@ var locktimer = {
         if(!$('dw__editform')) return;
         locktimer.pageid = $('dw__editform').elements.id.value;
         if(!locktimer.pageid) return;
-        if($('wiki__text').readOnly) return;
 
         // init ajax component
         locktimer.sack = new sack(DOKU_BASE + 'lib/exe/ajax.php');