strongly-typed 0e5b5b46a8 Fix regression with XML output.
Copy-paste error from 9edcc44.

Spotted with `cd test && ./generate-xml.sh test-frames`

    --- test-frames/manual_frame2.xml	2016-05-09 00:19:44.000000000 +0200
    +++ test-frames/manual_frame2.xml.new	2016-05-09 01:09:09.000000000 +0200
    @@ -17,7 +17,7 @@
         <DataRecord id="1">
             <Function>Actual value</Function>
             <Unit>reserved but historic</Unit>
    -        <Value>135</Value>
    +        <Value>1</Value>
         </DataRecord>
    
     </MBusData>
2016-05-09 01:11:23 +02:00
..
2012-07-19 22:34:03 +02:00
2013-09-13 17:53:33 +02:00
2013-09-13 17:53:33 +02:00