fix: optimization.minimizer only access default with '...' at the end...

[yulodl]

#12733

[webpack-bot]

For maintainers only:

• This needs to be documented (issue in webpack/webpack.js.org will be filed when merged)
• This needs to be backported to webpack 4 (issue will be created when merged)

[webpack-bot]

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[sokra]

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[webpack-bot]

Hi @yulodl.

Just a little hint from a friendly bot about the best practice when submitting pull requests:

Don't submit pull request from your own master branch. It's recommended to create a feature branch for the PR.

You don't have to change it for this PR, just make sure to follow this hint the next time you submit a PR.

[sokra]

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