WebpackOptionsValidationError

After updating my composer in laravel(backend) this the error I've encountered.

I already tried, uninstall and reinstall the webpackage, but it's still not working. I hope you can help me with resolving this. Thank you in advance.

Invalid configuration object. Webpack has been initialised using a configuration object that does not match the API schema. - configuration.entry should be one of these: function | object { : non-empty string | [non-empty string] } | non-empty string | [non-empty string] -> The entry point(s) of the compilation.
Details: * configuration.entry should be an instance of function -> A Function returning an entry object, an entry string, an entry array or a promise to these things. * configuration.entry['styles'] should be a string. -> The string is resolved to a module which is loaded upon startup. * configuration.entry['styles'] should not contain the item 'C:\xampp\htdocs\PlainTemplate\frontend\node_modules\bootstrap\dist\css\bootstrap.min.css' twice. * configuration.entry should be a string. -> An entry point without name. The string is resolved to a module which is loaded upon startup. * configuration.entry should be an array: [non-empty string] WebpackOptionsValidationError: Invalid configuration object. Webpack has been initialised using a configuration object that does not match the API schema. - configuration.entry should be one of these: function | object { : non-empty string | [non-empty string] } | non-empty string | [non-empty string] -> The entry point(s) of the compilation.
Details: * configuration.entry should be an instance of function -> A Function returning an entry object, an entry string, an entry array or a promise to these things. * configuration.entry['styles'] should be a string. -> The string is resolved to a module which is loaded upon startup. * configuration.entry['styles'] should not contain the item 'C:\xampp\htdocs\PlainTemplate\frontend\node_modules\bootstrap\dist\css\bootstrap.min.css' twice. * configuration.entry should be a string. -> An entry point without name. The string is resolved to a module which is loaded upon startup. * configuration.entry should be an array: [non-empty string] at webpack (C:\xampp\htdocs\PlainTemplate\frontend\node_modules\webpack\lib\webpack.js:31:9) at Observable.rxjs_1.Observable.obs [as _subscribe] (C:\xampp\htdocs\PlainTemplate\frontend\node_modules@angular-devkit\build-webpack\src\webpack-dev-server\index.js:37:37) at Observable._trySubscribe (C:\xampp\htdocs\PlainTemplate\frontend\node_modules\rxjs\internal\Observable.js:44:25) at Observable.subscribe (C:\xampp\htdocs\PlainTemplate\frontend\node_modules\rxjs\internal\Observable.js:30:22) at C:\xampp\htdocs\PlainTemplate\frontend\node_modules\rxjs\internal\util\subscribeTo.js:22:31 at Object.subscribeToResult (C:\xampp\htdocs\PlainTemplate\frontend\node_modules\rxjs\internal\util\subscribeToResult.js:10:45) at MergeMapSubscriber._innerSub (C:\xampp\htdocs\PlainTemplate\frontend\node_modules\rxjs\internal\operators\mergeMap.js:82:29) at MergeMapSubscriber._tryNext (C:\xampp\htdocs\PlainTemplate\frontend\node_modules\rxjs\internal\operators\mergeMap.js:76:14) at MergeMapSubscriber._next (C:\xampp\htdocs\PlainTemplate\frontend\node_modules\rxjs\internal\operators\mergeMap.js:59:18) at MergeMapSubscriber.Subscriber.next (C:\xampp\htdocs\PlainTemplate\frontend\node_modules\rxjs\internal\Subscriber.js:67:18) at TapSubscriber._next (C:\xampp\htdocs\PlainTemplate\frontend\node_modules\rxjs\internal\operators\tap.js:65:26) at TapSubscriber.Subscriber.next (C:\xampp\htdocs\PlainTemplate\frontend\node_modules\rxjs\internal\Subscriber.js:67:18) at MergeMapSubscriber.notifyNext (C:\xampp\htdocs\PlainTemplate\frontend\node_modules\rxjs\internal\operators\mergeMap.js:92:26) at InnerSubscriber._next (C:\xampp\htdocs\PlainTemplate\frontend\node_modules\rxjs\internal\InnerSubscriber.js:28:21) at InnerSubscriber.Subscriber.next (C:\xampp\htdocs\PlainTemplate\frontend\node_modules\rxjs\internal\Subscriber.js:67:18) at ForkJoinSubscriber.notifyComplete (C:\xampp\htdocs\PlainTemplate\frontend\node_modules\rxjs\internal\observable\forkJoin.js:82:25)

from Newest questions tagged laravel-5 - Stack Overflow http://bit.ly/2WalGj5
via IFTTT