dynare_solve.m: return with valid solution even if Jacobian is ill-behaved

In pathological cases, the Jacobian at the initial but true steady state value is ill-behaved. In this case we should return with the valid steady state instead of trying random starting values

matlab/dynare_solve.m

@@ -78,6 +78,10 @@ if jacobian_flag
     wrong_initial_guess_flag = false;
     if ~all(isfinite(fvec)) || any(isinf(fjac(:))) || any(isnan((fjac(:)))) ...
             || any(~isreal(fvec)) || any(~isreal(fjac(:)))
+        if max(abs(fvec)) < tolf %return if initial value solves problem
+            info = 0; 
+            return;
+        end    
         disp('Randomize initial guess...')
         % Let's try random numbers for the variables initialized with the default value.
         wrong_initial_guess_flag = true;