bug: form not always avail looking for 1st row

LinkedIn - Demo Form Autofill.html

@@ -3,7 +3,7 @@
     var fillScript = document.createElement('script'), // the LI autofill script (client-side)
       iframeHolderDiv = document.createElement('div'), // so we can style location of button
       autoFillLocation = document.querySelector("form[id^='mktoForm_']"), // will only find first Marketo form on a page
-      firstRow = document.querySelector('form .mktoFormRow'),
+      firstRow,
       mktoForm,
       hiddenLinkedInInputs = document.createDocumentFragment(), // since we're creating multiple nodes, just do the add once
       hiddenInputCreator = function (tagName, onChangeHandler) {
@@ -324,6 +324,7 @@
         // need the id of the form so we can hook up autofill
         // doing this way will work on any Marketo form
         fillScript.setAttribute('data-form', 'mktoForm_' + form.getId());
+        firstRow = document.querySelector('form .mktoFormRow');  // so we can use it above
         mktoForm = form;  // so we can use it above
         form.onSubmit(function (form) {
           // tell GA about it, but only if we know they autofilled