largefiles: avoid use of uinitialized variable in case of errors

hgext/largefiles/overrides.py

@@ -619,10 +619,12 b' def override_archive(orig, repo, dest, n'
             f = lfutil.splitstandin(f)
 
             def getdatafn():
+                fd = None
                 try:
                     fd = open(path, 'rb')
                     return fd.read()
                 finally:
+                    if fd:
                     fd.close()
 
             getdata = getdatafn