Bad text wrapping with widow control enabled

[pgundlach]

<Layout
  xmlns="urn:speedata.de:2009/publisher/en"
  xmlns:sd="urn:speedata:2009/publisher/functions/en"
  version="3.3.9">

  <SetGrid height="12pt" nx="12"/>
  <Trace grid="yes"/>

  <SetVariable variable="ht" select="8"/>
  <Pagetype name="x" test="true()">
    <Margin left="1cm" right="1cm" top="1cm" bottom="1cm"/>
    <PositioningArea name="f">
      <PositioningFrame width="5" height="{$ht}" row="1" column="1"/>
      <PositioningFrame width="5" height="{$ht}" row="1" column="7"/>
    </PositioningArea>
  </Pagetype>
  
  <Record element="data">
    <PlaceObject row="1" column="10">
      <Box width="2" height="5" backgroundcolor="lightgreen"/>
    </PlaceObject>
    <Output area="f" allocate="auto">
      <Text>
        <Paragraph>
          <Value select="sd:dummytext()"/>
        </Paragraph>
      </Text>
    </Output>
  </Record>
</Layout>

gives this result: