Formhandler

I've got the following checkboxes:

<input type="checkbox" id="topic1" name="contact[topics][]" value="topic1"/><label for="topic1">Topic 1</label>
<input type="checkbox" id="topic2" name="contact[topics][]" value="topic2"/><label for="topic2">Topic 2</label>
<input type="checkbox" id="topic3" name="contact[topics][]" value="topic3"/><label for="topic3">Topic 3</label>

In my Mail-Template i've got a subpart, which should only be displayed, if at least one topic-checkbox ist checked.

<!-- ###ISSET_topics### -->
###LLL:topics###: ###value_topics###
<!-- ###ISSET_topics### -->

This subpart will never be shown.
I think the handleIssetSubpartCondition-method in the Tx_Formhandler_View_Form-Class doesn't handle array-values properly.
It calls tslib_cObj->getGlobal to retrieve the fields value, which will never return an array because of the "is_scalar"-Check.

Tx_Formhandler_View_Form

protected function handleIssetSubpartCondition($condition) {
    $fieldname = $condition;
    $negate = FALSE;
    if(substr($condition, 0, 1) === '!') {
        $fieldname = substr($condition, 1);
        $negate = TRUE;
    }
    $value = $this->globals->getCObj()->getGlobal($fieldname, $this->gp);
    if(is_array($value)) {
        $result = (empty($value));
    }

...

t3lib_cObj->getGlobal

function getGlobal($keyString, $source = NULL) {
    $keys = explode('|', $keyString);
    $numberOfLevels = count($keys);
    $rootKey = trim($keys[0]);
    $value = isset($source) ? $source[$rootKey] : $GLOBALS[$rootKey];

    ...

    if (!is_scalar($value)) {
        $value = '';
    }
    return $value;
}