Running readme code yields error

[paniash]

Hi!

I'm trying to run the code written under the usage section in the README but I get the following error:

[ins] In [1]: from qutip.piqs import Dicke

[ins] In [2]: from qutip import steadystate

[ins] In [3]: N = 10

[ins] In [4]: system = Dicke(N, emission=1, pumping=3)

[ins] In [5]: L = system.liouvillian()

[ins] In [6]: steady = steadystate(L)
---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
<ipython-input-6-032c9e7074e5> in <module>
----> 1 steady = steadystate(L)

~/.local/lib/python3.9/site-packages/qutip/steadystate.py in steadystate(A, c_op_list, method, solver, **kwargs)
    273         if (ss_args['solver'] == 'scipy' and ss_args['sparse']) \
    274                 or ss_args['solver'] == 'mkl':
--> 275             return _steadystate_direct_sparse(A, ss_args)
    276         else:
    277             return _steadystate_direct_dense(A, ss_args)

~/.local/lib/python3.9/site-packages/qutip/steadystate.py in _steadystate_direct_sparse(L, ss_args)
    418         orig_nnz = L.nnz
    419         _direct_start = time.time()
--> 420         lu = splu(L, permc_spec=ss_args['permc_spec'],
    421                   diag_pivot_thresh=ss_args['diag_pivot_thresh'],
    422                   options=dict(ILU_MILU=ss_args['ILU_MILU']))

/usr/lib/python3.9/site-packages/scipy/sparse/linalg/dsolve/linsolve.py in splu(A, permc_spec, diag_pivot_thresh, relax, panel_size, options)
    335         _options["SymmetricMode"] = True
    336
--> 337     return _superlu.gstrf(N, A.nnz, A.data, A.indices, A.indptr,
    338                           csc_construct_func=csc_construct_func,
    339                           ilu=False, options=_options)

RuntimeError: Factor is exactly singular