"Execute Script (R) output data importing bug?"

The process

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<process version="5.3.008">
  <context>
    <input/>
    <output/>
    <macros/>
  </context>
  <operator activated="true" class="process" compatibility="5.3.008" expanded="true" name="Process">
    <process expanded="true">
      <operator activated="true" class="r:execute_script_r" compatibility="5.3.000" expanded="true" height="76" name="Execute Script (R)" width="90" x="179" y="120">
        <parameter key="script" value="&#10;output &lt;- data.frame(att1=c(NA,NA))&#10;&#10;print(names(output))"/>
        <enumeration key="inputs"/>
        <list key="results">
          <parameter key="output" value="Data Table"/>
        </list>
      </operator>
      <connect from_op="Execute Script (R)" from_port="output 1" to_port="result 1"/>
      <portSpacing port="source_input 1" spacing="0"/>
      <portSpacing port="sink_result 1" spacing="0"/>
      <portSpacing port="sink_result 2" spacing="0"/>
    </process>
  </operator>
</process>

results in the error: "In order to import an R Data Frame as example set the data frame must provide attribute names."
even though the (only) attribute is named. This only seems to happen if all data in some attribute is NA.