TypeError: Cannot read property 'length' of undefined

[skull-squadron]

In an untitled editor:

package.coffee:395 Error serializing package 'pp' TypeError: Cannot read property 'length' of undefined
    at Object.serialize ({{redacted}}/.atom/packages/pp/lib/pp.coffee:489:5)
    at Package.module.exports.Package.serialize (/Applications/Atom-Beta.app/Contents/Resources/app.asar/src/package.js:643:97)
    at PackageManager.module.exports.PackageManager.serializePackage (/Applications/Atom-Beta.app/Contents/Resources/app.asar/src/package-manager.js:606:63)
    at PackageManager.module.exports.PackageManager.serialize (/Applications/Atom-Beta.app/Contents/Resources/app.asar/src/package-manager.js:599:14)
    at AtomEnvironment.module.exports.AtomEnvironment.serialize (/Applications/Atom-Beta.app/Contents/Resources/app.asar/src/atom-environment.js:800:38)
    at /Applications/Atom-Beta.app/Contents/Resources/app.asar/src/atom-environment.js:1005:27
    at AtomEnvironment.module.exports.AtomEnvironment.saveState (/Applications/Atom-Beta.app/Contents/Resources/app.asar/src/atom-environment.js:1001:14)
    at /Applications/Atom-Beta.app/Contents/Resources/app.asar/src/atom-environment.js:314:28module.exports.Package.serialize @ package.coffee:395module.exports.PackageManager.serializePackage @ package-manager.coffee:494module.exports.PackageManager.serialize @ package-manager.coffee:490module.exports.AtomEnvironment.serialize @ atom-environment.coffee:710(anonymous function) @ atom-environment.coffee:858module.exports.AtomEnvironment.saveState @ atom-environment.coffee:856(anonymous function) @ atom-environment.coffee:241