This is a good one. Introduced in v0.93. I can't reproduce this bug in neither Chrome nor Safari, but only on iPhone.
The Forms example at throws an error when rendering the NumberField in it and doesn't render anything that goes after it. I created a simple page and got the same error:
HTML Code:
<!DOCTYPE html>
    <meta charset="utf-8" />
    <link rel="stylesheet" type="text/css" href="/touch/resources/css/ext-touch.css" />
    <script type="text/javascript" src="/touch/ext-touch-debug.js"></script>
    <script type="text/javascript">
            onReady: function() {
                var form = new Ext.form.FormPanel({
                    fullscreen: true,
                    items: [{
                        xtype: 'fieldset',
                        title: 'Number Field',
                        items: [{
                            xtype: 'numberfield'
The error is:
JavaScript Error on Line 13488 in ext-touch-debug.js
TypeError: Result of expression 'item' [null] is not an object.