bug: minus_logged_prior_density.m: fix expected dimension of unused output arguments

Hessian needs to be empty for newrat

(cherry picked from commit 7f5d8b81)

matlab/minus_logged_prior_density.m

@@ -30,8 +30,8 @@ function [fval,info,exit_flag,fake_1,fake_2] = minus_logged_prior_density(xparam
 % You should have received a copy of the GNU General Public License
 % along with Dynare.  If not, see <https://www.gnu.org/licenses/>.
 
-fake_1 = 1;
-fake_2 = 1;
+fake_1 = [];
+fake_2 = [];
 
 exit_flag = 1;
 info = zeros(4,1);