ERROR in OfflinePlugin: Something went wrong with ServiceWorker entry

webpack.base.config.js

"use strict";

var OfflinePlugin = require("offline-plugin");

var path = require("path");

module.exports = {
  context: path.join(__dirname, "src"),
  entry: {
    app: "./index.js",
    vendor: ["./Vendor1.js"]
  },
  output: {
    path: path.join(__dirname, "dist"),
    filename: "[name].[chunkhash].js",
    chunkFilename: "[name].chunck.[chunkhash].js"
  },
  plugins: [
    new OfflinePlugin()
  ]
};