Diff sometimes fails with error "pop from empty list"

[JohnLudlow]

Hi,

There is one file on one revision which gives me this error when I try to diff with qdiff:

bzr: ERROR: exceptions.IndexError: pop from empty list

Traceback (most recent call last):
  File "C:/Program Files (x86)/Bazaar/plugins\qbzr\lib\trace.py", line 300, in reports_exception_decorate
  File "C:/Program Files (x86)/Bazaar/plugins\qbzr\lib\diffwindow.py", line 235, in initial_load
  File "bzrlib\cleanup.pyo", line 131, in run
  File "bzrlib\cleanup.pyo", line 165, in _do_with_cleanups
  File "C:/Program Files (x86)/Bazaar/plugins\qbzr\lib\diffwindow.py", line 248, in _initial_load
  File "C:/Program Files (x86)/Bazaar/plugins\qbzr\lib\diffwindow.py", line 404, in load_diff
  File "C:/Program Files (x86)/Bazaar/plugins\qbzr\lib\diffview.py", line 435, in append_diff
  File "C:/Program Files (x86)/Bazaar/plugins\qbzr\lib\diffview.py", line 384, in insertIxsWithChangesHighlighted
IndexError: pop from empty list

bzr 2.2.1 on python 2.6.4 (win32)
arguments: ['C:\\Program Files (x86)\\Bazaar\\bzrw.exe', 'qlog']
encoding: 'cp1252', fsenc: 'mbcs', lang: None
plugins:
  bzrtools C:\Program Files (x86)\Bazaar\plugins\bzrtools [2.2.0]
  colo C:\Program Files (x86)\Bazaar\plugins\colo [0.1.0]
  explorer C:\Program Files (x86)\Bazaar\plugins\explorer [1.1.1]
  fastimport C:\Program Files (x86)\Bazaar\plugins\fastimport [0.9.0dev]
  launchpad C:\Program Files (x86)\Bazaar\plugins\launchpad [2.2.1]
  loom C:\Program Files (x86)\Bazaar\plugins\loom [2.2.1dev]
  netrc_credential_store C:\Program Files (x86)\Bazaar\plugins\netrc_credential_store [2.2.1]
  news_merge C:\Program Files (x86)\Bazaar\plugins\news_merge [2.2.1]
  pipeline C:\Program Files (x86)\Bazaar\plugins\pipeline [unknown]
  qbzr C:\Program Files (x86)\Bazaar\plugins\qbzr [0.19.2]
  rewrite C:\Program Files (x86)\Bazaar\plugins\rewrite [0.6.1]
  svn C:\Program Files (x86)\Bazaar\plugins\svn [1.0.4]
  upload C:\Program Files (x86)\Bazaar\plugins\upload [1.0.0dev]
  xmloutput C:\Program Files (x86)\Bazaar\plugins\xmloutput [0.8.6]

Earlier and later revisions are fine, and other files are fine, it's just that file in that revision. The first few times this happened, it just flashed up then died. I was able to diff and commit with the CLI tools, and now if I try to diff that file again, I get the above error.

If required, I can supply copies of the file on the failing revision as well as before and after.

Thanks