Description of problem:
The normal meld behaviour that, when you're using an SVN checkout, automatically diffs a modified file in a working copy against the base revision, isn't working in Fedora 13.

Version-Release number of selected component (if applicable):
meld-1.3.1-1.fc13.noarch

How reproducible:
Always

Steps to Reproduce:
1. Check out an SVN working copy from an SVN repository somewhere
2. Modify a file (let's call it "foo")
3. Run "meld foo" from the working copy directory

Actual results:
Meld opens with a blank screen. Console shows:
Traceback (most recent call last):
  File "/usr/share/meld/task.py", line 130, in iteration
    ret = task()
  File "/usr/share/meld/vcview.py", line 353, in run_diff_iter
    diff = difffunc()
  File "/usr/share/meld/vcview.py", line 419, in _command_iter
    r = readfunc()
  File "/usr/share/meld/misc.py", line 209, in __call__
    self.proc = subprocess.Popen(command, cwd=workdir, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
  File "/usr/lib64/python2.6/subprocess.py", line 621, in __init__
    errread, errwrite)
  File "/usr/lib64/python2.6/subprocess.py", line 1126, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory: ''


Expected results:
Meld opens the file "foo", showing the difference between the modified version and the original one as checked out.