The `findInputs` method is killing IE7

I've noticed that the `findInputs` method is throwing a fatal error in IE7 when the form it's called on has direct children which aren't `input`s. 

For example: we're using Twitter Bootstrap which calls for the following type of structure...

    <form class="form-horizontal">
        <div class="control-group">
            <label class="span2 control-label">Card Number</label>

            <div class="preSpan2 controls">
                <input class="span5 cardNumber" type="text" autocomplete="off" data-encrypted-name="number" />
            </div>
        </div>
    </form>

When you submit the form in IE7 you get `Unable to get value of the property 'data-encrypted-name': object is null or undefined`.