[eigen] SEGV in eigen Cholmod

[Robert Lupton the Good <rhl@xxxxxxxxxxxxxxxxxxx>]

We got a SEGV from eigen;  I think that the underlying problem is in our inputs, but the error handling in eigen causes a bad pointer.

I see that there's a bug report
	https://bitbucket.org/eigen/eigen/pull-requests/395/cholmod-error-handling/diff?
which sounds similar -- is there any progress on this?  Is it at the point where someone (maybe my telescope project, the LSST?) could get this finished and accepted and merged?

In case this is a new report, the problem:

In Eigen/src/CholmodSupport/CholmodSupport.h:294
      m_cholmodFactor = internal::cm_analyze<StorageIndex>(A, m_cholmod);

If the `cm_analyze` call fails, then m_cholmodFactor is NULL and 
Eigen/src/CholmodSupport/CholmodSupport.h:276
      factorize(matrix);
results in a SEGV.

							R