"installedCssChunks is not defined" after 2.9.0 update

[michaelfaith]

After upgrading from 2.8.1 to 2.9.0 (and then 2.9.1), we're seeing this error repeatedly in the Chrome dev console. We didn't change any aspect of our config or css loading set-up.

I believe this is related to this change: https://github.com/webpack-contrib/mini-css-extract-plugin/pull/1043

Plugin config

...
  {
        test: /\.less$/,
        include: [path.join(appDirectory, 'stylesheets')],
        exclude: [],
        use: [
          MiniCssExtractPlugin.loader,
          {
            loader: 'css-loader',
            options: {
              sourceMap: DEV,
            },
          },
          {
            loader: 'postcss-loader',
            options: {
              postcssOptions: {
                plugins: [require('autoprefixer')],
              },
              sourceMap: DEV,
            },
          },

          {
            loader: 'less-loader',
            options: {
              lessOptions: {
                math: 'always',
              },
              sourceMap: DEV,
            },
          },
        ],
      },
...
plugins: [
   ...
  new MiniCssExtractPlugin({
      experimentalUseImportModule: true,
      filename: '[name].[contenthash:20].css',
    }),
  ...
]

Please paste the results of npx webpack-cli info here, and mention other relevant information

System:
    OS: macOS 14.6.1
    CPU: (12) arm64 Apple M3 Pro
    Memory: 1.10 GB / 36.00 GB
  Binaries:
    Node: 20.12.2 - ~/.nvm/versions/node/v20.12.2/bin/node
    npm: 10.8.2 - ~/.nvm/versions/node/v20.12.2/bin/npm
  Browsers:
    Chrome: 127.0.6533.120
    Safari: 17.6
  Packages:
    babel-loader: ^9.1.3 => 9.1.3 
    css-loader: ^6.11.0 => 6.11.0 
    expose-loader: ^5.0.0 => 5.0.0 
    json-loader: ~0.5.7 => 0.5.7 
    less-loader: ^12.2.0 => 12.2.0 
    postcss-loader: ^8.1.1 => 8.1.1 
    source-map-loader: ^5.0.0 => 5.0.0 
    style-loader: ^4.0.0 => 4.0.0 
    webpack: ^5.93.0 => 5.93.0 
    webpack-cli: ^5.1.4 => 5.1.4