I'm posting this to the mailing list first because I'm not sure I've
fixed this correctly. This is a patch for a bug in ticker.py.
In Autolocator.get_locator, if the distance passed in is 0, the call to
log10 will crash with an overflow error. I think I'm hitting this
problem because I plot a lot of binary data, and the first plot when
this happened, consisted of all zeros (giving the y axis no distance - I
could be talking complete nonsense, I haven't really examined the
code). What I'm not sure about is, in the case that distance is 0,
should the variable ld be set to 0 (as I have done in the attached
patch), or is another value more sensible?