Lets try this...

www/pad/wysiwygarea-plugin.js

@@ -471,9 +471,16 @@
                     // CryptPad
                     var _iframe = window._iframe = iframe.$;
 					var fw = this;
-					_iframe.contentWindow.onload = function () {
+					_iframe.contentWindow.onload = function () {}
+                    var intr = setInterval(function () {
+                        //console.log(_iframe.contentWindow.document.body);
+						if (!_iframe.contentWindow) { return; }
+						if (!_iframe.contentWindow.document) { return; }
+						if (_iframe.contentWindow.document.readyState !== 'complete') { return; }
+						if (!_iframe.contentWindow.document.getElementsByTagName('title').length) { return; }
+						clearInterval(intr);
 						CKEDITOR.tools.callFunction(fw._.frameLoadedHandler, _iframe.contentWindow);
-					};
+                    }, 10);
                     return;
 
 					// Work around Firefox bug - error prune when called from XUL (http://dev.ckeditor.com/ticket/320),