py-pdbtrack-grub-for-buffer assigns and reads the
global variable "buf". It binds "curbuf" in a let
statement, but never uses that variable. I think that
the intent was to create a local binding and use it.
The enclosed patch changes the binding so that the
variable name "buf" is used throughout the function.
I have not tested this. I might be missing something
subtle. I stumbled across this bug when I looked at
the warnings produced by Emacs 21.2 while