fix(modal): ensure that the full screen height is calculated correctly

Vben

2021-06-11 1c1755cf5b4ada7263c05ddf4105abb52a2abb2f

 src/components/Modal/src/components/ModalFooter.vue

@@ -33,6 +33,7 @@
      function handleCancel(e: Event) {
        emit('cancel', e);
      }

      return { handleOk, handleCancel };
    },
  });