Group containing single optional decimal with always present exponent operator and optionally present mantissa operator does not create presence map

Given the template below, a presence map should always be encoded due to the mantissa operator requiring a presence map. However, the presence map is never encoded and the mantissa is unable to decode the value properly.

<template>
<group name="grp">
<decimal name="dcml" presence="optional">
<exponent><delta/></exponent>
<mantissa><copy/></mantissa>
</decimal>
</group>
</template>

See FAST discussion at FPL Forums: http://fixprotocol.org/discuss/read/8e1d2cc9