Remove unnecessary space in data_combo title

In theme_date_combo(), the fieldset's title is generated as follows:

'#title' => field_filter_xss(t($element['#title'])) . ' ' . ($element['#delta'] > 0 ? intval($element['#delta'] + 1) : ''),

When #delta is 0, the space after the title is unnecessary. The problem with this is that the fieldset title will not be empty even if $element['#title'] is empty. As a result, a seemingly empty <legend> tag will be rendered in the fieldset theme, which may produce an undesirable look.
I'm attaching a patch to address this.