locate.pyx: scipy.optimize: invalid value encountered in subtract

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I have been getting this warning quite a bit when relocating very large catalogs. I think it is harmless but it can be a bit distracting.

../scipy/optimize/_numdiff.py:686: RuntimeWarning: invalid value encountered in subtract
  df = [f_eval - f0 for f_eval in f_evals]

I think I finally traced it back to rms in locate.pyx

        if valid_measurements == 0:
            return np.inf

it seems optimize prefers that to just return a "very large RMS" if there are no valid arrivals so it is working with small but still non-zero numbers. I just changed it to return 1e6 and all the warnings went away. For the little it's worth!