indexFileName not in assets

[Hideyoshi]

webpack version: 5.7.0
antd-theme-webpack-plugin version: 1.3.9

generateIndexContent(assets, compilation) {
console.log(this.options.indexFileName) // index.html (defaultOption)
console.log(this.options.indexFileName in assets) // false
if (
this.options.indexFileName &&
this.options.indexFileName in assets
) {
......
}
......
}

It cause the generateIndexContent callback not working.
But it working when plugin's version is 1.3.7