TypeError: Cannot convert undefined or null to object

[59naga]

broken If the default is undefined.

'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});
var foo = 'bar';
exports.foo = foo;
module.exports = Object.assign(exports.default, exports);

babel index.js --presets es2015 --plugins add-module-exports > bundle.js
# 'use strict';
#
# Object.defineProperty(exports, "__esModule", {
#   value: true
# });
# var foo = 'bar';
# exports.foo = foo;
# module.exports = Object.assign(exports.default, exports);

node bundle.js
# module.exports = Object.assign(exports.default, exports);
#                         ^

# TypeError: Cannot convert undefined or null to object
#     at Function.assign (native)
# ...