Added fallthrough case for to_super to catch bugs elsewhere.
Added fallthrough case for to_super to catch bugs elsewhere.

anubhavvardhan/qutip,cgranade/qutip,cgranade/qutip,zasdfgbnm/qutip,zasdfgbnm/qutip,qutip/qutip,anubhavvardhan/qutip,qutip/qutip