fix_cascade_export (#1897)

tools/export_utils.py

@@ -109,7 +109,7 @@ def dump_infer_config(config, path, image_shape, model):
             'Architecture: {} is not supported for exporting model now'.format(
                 infer_arch))
         os._exit(0)
-    if 'mask_post_process' in model.__dict__:
+    if getattr(model.__dict__, 'mask_post_process', None):
         infer_cfg['mask_resolution'] = model.mask_post_process.mask_resolution
     infer_cfg['with_background'], infer_cfg['Preprocess'], infer_cfg[
         'label_list'], image_shape = parse_reader(