Uncaught TypeError: Cannot read property 'delete' of undefined

[geeksville]

steps to repro:

1. Launch "atom ." (from a new install of either atom or atom-beta downloaded as a deb today from your website) intending to open the project in the current directory
2. Any files opened raise this dialog and the file content is blank.
3. If you instead launch "atom" the problem does not occur

Atom: 1.20.0-beta5 x64
Electron: 1.6.9
OS: Ubuntu 16.04.3
Thrown From: tabs package 0.107.0

Stack Trace

Uncaught TypeError: Cannot read property 'delete' of undefined

At /usr/share/atom-beta/resources/app/src/text-editor-component.js:1441

TypeError: Cannot read property 'delete' of undefined
    at TextEditorComponent.didDetach (/usr/share/atom-beta/resources/app/src/text-editor-component.js:1441:48)
    at HTMLElement.detachedCallback (/usr/share/atom/resources/app/src/text-editor-element.js:47:25)
    at HTMLElement.PaneElement.itemRemoved (/usr/share/atom/resources/app/src/pane-element.js:187:29)
    at Function.module.exports.Emitter.simpleDispatch (/usr/share/atom-beta/resources/app/node_modules/event-kit/lib/emitter.js:25:20)
    at Emitter.module.exports.Emitter.emit (/usr/share/atom-beta/resources/app/node_modules/event-kit/lib/emitter.js:141:34)
    at Pane.module.exports.Pane.removeItem (/usr/share/atom-beta/resources/app/src/pane.js:634:26)
    at Pane.module.exports.Pane.destroyItem (/usr/share/atom-beta/resources/app/src/pane.js:706:22)
    at TabBarView.module.exports.TabBarView.closeTab (/usr/share/atom-beta/resources/app/node_modules/tabs/lib/tab-bar-view.js:341:32)
    at HTMLDivElement.TabView.didClickCloseIcon (/usr/share/atom-beta/resources/app/node_modules/tabs/lib/tab-bar-view.js:229:25)

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