[Kst] [Kst-plot/kst] f96f3e: Avoid crashes when plots are given bad data.

[Barth Netterfield]

  Branch: refs/heads/master
  Home:   https://github.com/Kst-plot/kst
  Commit: f96f3e1741dc64ee182e404d80fc09a1fd84aea9
      https://github.com/Kst-plot/kst/commit/f96f3e1741dc64ee182e404d80fc09a1fd84aea9
  Author: Barth Netterfield <netterfield at astro.utoronto.ca>
  Date:   2016-06-29 (Wed, 29 Jun 2016)

  Changed paths:
    M src/libkstapp/plotaxis.cpp
    M src/libkstapp/plotrenderitem.cpp
    M src/libkstapp/plotrenderitem.h

  Log Message:
  -----------
  Avoid crashes when plots are given bad data.

Looks for nans, infs, too small and too large
limits and ranges, as you might end up with
when plotting corrupted telemetry data.