CubePlotCurve.h: 2012-01-30 Steven Lambright - Fixed a bug added when the...

CubePlotCurve.h: 2012-01-30 Steven Lambright - Fixed a bug added when the legendItem() method was removed. This method is necessary. Fixes #688. 

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@3994 41f8697f-d340-4b68-9986-7bafba869bb8