6d0f6e6573a34d59107a033f12e9c9ad3ab0604e Fix an invalid memory access in k_order_perturbation DLL.

================================ DYNARE MAKE CHECK MATLAB RESULTS ================================ | TOTAL: 423 | PASS: 418 | FAIL: 3 | XFAIL: 2 | XPASS: 0 | LIST OF FAILED TESTS: | * k_order_perturbation/fs2000k2_use_dll.mod | * k_order_perturbation/fs2000k_1_use_dll.mod | * k_order_perturbation/fs2000k3_use_dll.mod

================================ DYNARE MAKE CHECK OCTAVE RESULTS ================================ | TOTAL: 421 | PASS: 419 | FAIL: 0 | XFAIL: 2 | XPASS: 0

A full log can be found on karaba in '/tmp/dynare-4.4-check-mMEZ8RRouj.log'.