Fix name error introduced in c21d845836e4
c21d845836e4 use a ``vocab`` variable but doesn't define it. I assumed ``vocab`` is
``field.vocabulary(form)``.
<div id="ajaxroot">
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<script src="http://foo.js" type="text/javascript"> </script>
<link rel="stylesheet" type="text/css" media="all" href="qunit.css" />
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<h1>Hello</h1>
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