core: reset params pointers if there is a failure in parse_params()

- patch by Jijo

parser/parse_param.c

@@ -555,6 +555,7 @@ int parse_params(str* _s, pclass_t _c, param_hooks_t* _h, param_t** _p)
  error:
 	if (t) pkg_free(t);
 	free_params(*_p);
+	*_p = 0;
 	return -2;
 
  ok: