qlog: Can't show diff of renamed files in qlog ("Operation aborted")

[besy]

If you double-click a renamed file in qlog (should open qdiff), you get an error message: "File ... is not versioned. Operation aborted."

Steps to reproduce (in Windows, Bazaar 1.18):
md tmp
cd tmp
bzr init
<copy an non-empty text file "test.txt" to tmp>
bzr add test.txt
bzr commit
bzr rename test.txt testren.txt
edit testren.txt
<make some changes to "testren.txt", e.g. add a line>
bzr commit
bzr qlog
<double click the entry "test.txt => testren.txt">

Now you get the following error message: 'File "test.txt => testren.txt" is not versioned. Operation aborted.'

However, you can show the correct diff by calling qdiff directly (instead of using qlog):
bzr qdiff -r1..2 testren.txt