Bug fix.
Bug fix.

If doing an exact diagonalisation, then we still need the hamiltonian
matrix even if we're also doing a direct lanczos calculation (admittedly
a dumb combination, but it's tested in the test suite...).

hande-qmc/hande,ruthfranklin/hande,hande-qmc/hande,hande-qmc/hande,hande-qmc/hande,hande-qmc/hande