BUG: When a user adds a new contour via the UI (when auto_contours is False) the Range editor UI inserts a default new value which was zero. However, zero may not be in the actual data range and this will cause an exception.  Instead we now compute the default value and the Range trait uses that value which is always correct.
BUG: When a user adds a new contour via the UI (when auto_contours is
False) the Range editor UI inserts a default new value which was zero.
However, zero may not be in the actual data range and this will cause an
exception.  Instead we now compute the default value and the Range trait
uses that value which is always correct.


alexandreleroux/mayavi,liulion/mayavi,liulion/mayavi,dmsurti/mayavi,alexandreleroux/mayavi,dmsurti/mayavi