dynare_estimation_init.m: add file type to exist statement

matlab/estimation/dynare_estimation_init.m

@@ -149,7 +149,7 @@ if ~isempty(bayestopt_) && any(bayestopt_.pshape==0) && any(bayestopt_.pshape~=0
     error('Estimation must be either fully ML or fully Bayesian. Maybe you forgot to specify a prior distribution.')
 end
 % Check if a _prior_restrictions.m file exists
-if exist([M_.fname '_prior_restrictions.m'])
+if exist([M_.fname '_prior_restrictions.m'],'file')
     options_.prior_restrictions.status = 1;
     options_.prior_restrictions.routine = str2func([M_.fname '_prior_restrictions']);
 end