[DOM Crawler] Forms->getUri() returns incorrect value when having no action attribute and having get parameters in the original URI

[thijsBreker]

When having a form like this

<form method="get">
    <input type="checkbox" name="checkbox" value="x"/>
    <input type="text" name="field" value="y"/>
    <input type="submit"/>
</form>

On a page with the URL http://localhost/foo/bar?checkbox=x&text=y when I change the value of the text field to z and un-check the checkbox the URI returned by Form->getUri() is http://localhost/foo/bar?checkbox=x&text=y&text=z instead of the expected http://localhost/foo/bar?text=z