cmd/uninstall: handle unparsed arguments.
cmd/uninstall: handle unparsed arguments.

If `Homebrew.args` hasn't yet been populated then `named` will return
`nil`. Instead, ensure it is an array before we try to `join` it.

This is pretty much only a test-time problem but has been causing flaky
builds.

reitermarkus/brew,JCount/brew,vitorgalvao/brew,EricFromCanada/brew,Homebrew/brew,sjackman/homebrew,mahori/brew,EricFromCanada/brew,mahori/brew,mahori/brew,claui/brew,nandub/brew,vitorgalvao/brew,nandub/brew,mahori/brew,claui/brew,Homebrew/brew,MikeMcQuaid/brew,konqui/brew,sjackman/homebrew,vitorgalvao/brew,sjackman/homebrew,JCount/brew,reitermarkus/brew,claui/brew,konqui/brew,Homebrew/brew,reitermarkus/brew,nandub/brew,Homebrew/brew,claui/brew,konqui/brew,konqui/brew,MikeMcQuaid/brew,MikeMcQuaid/brew,vitorgalvao/brew,JCount/brew,sjackman/homebrew,MikeMcQuaid/brew,nandub/brew,EricFromCanada/brew,JCount/brew,EricFromCanada/brew,reitermarkus/brew