do changecheck JS for default edit form only

Ignore-this: 27e51f5d17946587742ca29f640baad

darcs-hash:20091107152648-7ad00-65c14f833fbb9fd66bffbe676ca659f63a4c8800.gz

lib/scripts/edit.js

@@ -277,6 +277,7 @@ function initChangeCheck(msg){
     var edit_text   = document.getElementById('wiki__text');
     if(!edit_text) return;
     if(edit_text.readOnly) return;
+    if(!$('dw__editform')) return;
 
     // add change check for links
     var links = document.getElementsByTagName('a');