Fix test files following change in the preprocessor when there is no parameter or exogenous

preprocessor @ 84d57393

-Subproject commit bf89cedd88eef94b9e45ebf7a0a43574a1e4a16a
+Subproject commit 84d57393dc3972f1c61be9f9047ecd517319a318

tests/on-the-fly/ex3.mod

@@ -31,7 +31,7 @@ if ~isequal(length(intersect(M_.endo_names, {'c'; 'y'; 'k'; 'b'; 'a'; 'h'})), 6)
    error('Endogenous variables are wrong.')
 end
 
-if isfield(M_, 'param_names')
+if length(M_.param_names) > 0
    error('Parameters are wrong.')
 end
 

tests/on-the-fly/ex4.mod

@@ -30,7 +30,7 @@ if ~isequal(length(intersect(M_.endo_names, {'c'; 'y'; 'k'; 'b'; 'a'})), 5)
    error('Endogenous variables are wrong.')
 end
 
-if isfield(M_, 'param_names')
+if length(M_.param_names) > 0
    error('Parameters are wrong.')
 end
 

tests/on-the-fly/ex5.mod

@@ -31,6 +31,6 @@ if ~isequal(length(intersect(M_.endo_names, {'D'; 'S'; 'p'})), 3)
    error('Endogenous variables are wrong.')
 end
 
-if isfield(M_, 'exo_names')
+if length(M_.exo_names) > 0
    error('Exogenous variables are wrong.')
 end