stiffness matrix not square when elastic input depth dependent

[VvanderHeiden]

When providing depth dependent elastic input (young, poisson, biot), the resulting stiffness matrix is not square anymore.
A square stiffness matrix is needed to map strain to stress consistently and used to calculate aseismic slip in td_solve.
Error:

Error using td_solve (line 21) K must be a square matrix

Error in calc_aseismic_slip (line 17) [tau_red, slip_red] = td_solve(islip, tauexc, 0, K); % tauexc: stress drop for islip, stress increase outside

Error in FaultSlip/calculate_fault_slip (line 62) [tau_slip_new, islip{i}, slip_timestep_new] = calc_aseismic_slip(L_new, tau_new, tau_f_new, mu_II, K);

Error in panther (line 79) parfor (i = 1 : n_members, matlab_workers)

Error in MultiFaultCalculator/run (line 40) parfor i = 1 : n

Error in run_panther_depth_dependent_wirdum (line 109) wirdum_stress = wirdum_stress.run;