Cube.h: 2011-07-08 Steven Lambright - getProjection() and getCamera() will now...

Cube.h: 2011-07-08 Steven Lambright - getProjection() and getCamera() will now return NULL if the cube is not open, instead of crashing, references #161  
CubeManager.h: 2011-06-08 Steven Lambright - Better handles the case when a Cube fails to open, fixes #161. 

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@2757 41f8697f-d340-4b68-9986-7bafba869bb8