Struct field with optional child element isn't parsed when child is missing

[srowen]

Consider:

<Foo>
    <Bar bing="123">
    </Bar>
    <Bar bing="345">
        <Baz/>
    </Bar>
</Foo>

Bar has an optional child element Baz. It turns out that when this child is missing, as in the first <Bar> tag, the element is skipped. This results in the array-valued Bar having 1 element, not 2.