fbbe98815b245b3840da8dc24e2767b463c2ec84 fixing bug introduced in commit 6eb3a3d when displaying theoretical moments for a model with a single exogenous variable

================================ DYNARE MAKE CHECK MATLAB RESULTS ================================ | TOTAL: 490 | PASS: 475 | FAIL: 12 | XFAIL: 3 | XPASS: 0 | LIST OF FAILED TESTS: | * optimal_policy/nk_ramsey.mod | * optimal_policy/nk_ramsey_expectation.mod | * optimal_policy/nk_ramsey_expectation_a.mod | * optimal_policy/Ramsey/ramsey_ex_initval.mod | * optimal_policy/Ramsey/ramsey_ex.mod | * optimal_policy/Ramsey/ramsey_ex_initval_AR2.mod | * steady_state/multi_leads.mod | * ep/rbc.mod | * ep/rbcii.mod | * deterministic_simulations/homotopy.mod | * stochastic_purely_forward/stochastic_purely_forward.mod | * stochastic_purely_forward/stochastic_purely_forward_with_static.mod

================================ DYNARE MAKE CHECK OCTAVE RESULTS ================================ | TOTAL: 484 | PASS: 465 | FAIL: 16 | XFAIL: 3 | XPASS: 0 | LIST OF FAILED TESTS: | * optimal_policy/nk_ramsey.mod | * optimal_policy/nk_ramsey_expectation.mod | * optimal_policy/nk_ramsey_expectation_a.mod | * optimal_policy/Ramsey/ramsey_ex_initval.mod | * optimal_policy/Ramsey/ramsey_ex.mod | * optimal_policy/Ramsey/ramsey_ex_initval_AR2.mod | * steady_state/multi_leads.mod | * identification/kim/kim2.mod | * identification/as2007/as2007.mod | * ep/rbc.mod | * ep/rbcii.mod | * deterministic_simulations/homotopy.mod | * stochastic_purely_forward/stochastic_purely_forward.mod | * stochastic_purely_forward/stochastic_purely_forward_with_static.mod | * ../matlab/@dseries/detrend.m#1 | * ../matlab/lyapunov_symm.m#1

A full log can be found on karaba in '/tmp/dynare-master-check-PH3T0Xl2w5.log'.