facadeModuleId error when enabling manifest option with rollup externals

[elwynelwyn]

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Describe the bug

When enabling the build.manifest option alongside the build.rollupOptions.external option an error is thrown when building

Reproduction

https://github.com/elwynelwyn/vite-manifest-with-externals

System Info

• vite version: 2.0.5
• Operating System: debian
• Node version: 12.14.1
• Package manager (npm/yarn/pnpm) and version: yarn@1.22.4

Logs (Optional if provided reproduction)

yarn build
yarn run v1.22.4
warning package.json: No license field
$ tsc && vite build
vite v2.0.5 building for production...
✓ 7 modules transformed.
rendering chunks (1)...

error during build:
TypeError: Cannot read property 'facadeModuleId' of undefined
    at getChunkName (/repos/vite-manifest-with-externals/node_modules/vite/dist/node/chunks/dep-e0f09032.js:26966:27)
    at /repos/vite-manifest-with-externals/node_modules/vite/dist/node/chunks/dep-e0f09032.js:26992:73
    at Array.map (<anonymous>)
    at createChunk (/repos/vite-manifest-with-externals/node_modules/vite/dist/node/chunks/dep-e0f09032.js:26992:59)
    at Object.generateBundle (/repos/vite-manifest-with-externals/node_modules/vite/dist/node/chunks/dep-e0f09032.js:27009:53)
    at /repos/vite-manifest-with-externals/node_modules/rollup/dist/shared/rollup.js:19049:25
error Command failed with exit code 1.

Note this is the same issue as #2006 which was closed due to no repro

[MinJieLiu]

still error

[vite:manifest] Cannot read property 'facadeModuleId' of undefined