fix negated literals in initial state

src/ast/parser_def.hpp

@@ -441,7 +441,7 @@ const auto atomic_formula_of_names_equality_def = (lit('(') >> lit('=')) > name
 const auto atomic_formula_of_names_def = atomic_formula_of_names_equality | atomic_formula_of_names_predicate;
 const auto ground_atom_def = atomic_formula_of_names;
 const auto negated_ground_atom_def = lit('(') >> keyword_lit("not") > atomic_formula_of_names >> lit(')');
-const auto ground_literal_def = ground_atom | negated_ground_atom;
+const auto ground_literal_def = negated_ground_atom | ground_atom;
 
 const auto initial_element_literals_def = ground_literal;
 const auto initial_element_timed_literals_def = (lit('(') >> lit("at") >> number) > ground_literal > lit(')');