Fix compilation error in HouseholderSequence introduced in my previous commit.
Fix compilation error in HouseholderSequence introduced in my previous commit.

rotorliu/eigen,rotorliu/eigen,rotorliu/eigen,mjbshaw/Eigen,madlib/eigen_backup,mjbshaw/Eigen,mjbshaw/Eigen,madlib/eigen_backup,mjbshaw/Eigen,madlib/eigen_backup,rotorliu/eigen,madlib/eigen_backup