Uncaught TypeError: Cannot read property 'length' of undefined

[Enter steps to reproduce:]

1. ...
2. ...

Atom: 1.27.2 x64
Electron: 1.7.15
OS: Mac OS X 10.13.5
Thrown From: rust-api-docs-helper package 0.5.1

Stack Trace

Uncaught TypeError: Cannot read property 'length' of undefined

At /Users/zhaoyue/.atom/packages/rust-api-docs-helper/lib/gutter-decorator.coffee:22

TypeError: Cannot read property 'length' of undefined
    at GutterDecorator.module.exports.GutterDecorator.updateMarkers (/packages/rust-api-docs-helper/lib/gutter-decorator.coffee:22:7)
    at /packages/rust-api-docs-helper/lib/gutter-decorator.coffee:1:1
    at Function.module.exports.Emitter.simpleDispatch (/Applications/Atom.app/Contents/Resources/app/node_modules/event-kit/lib/emitter.js:25:20)
    at Emitter.module.exports.Emitter.emit (/Applications/Atom.app/Contents/Resources/app/node_modules/event-kit/lib/emitter.js:141:34)
    at TextBuffer.module.exports.TextBuffer.emitDidStopChangingEvent (/Applications/Atom.app/Contents/Resources/app/node_modules/text-buffer/lib/text-buffer.js:1817:26)
    at later (/Applications/Atom.app/Contents/Resources/app/node_modules/text-buffer/lib/helpers.js:28:13)

Commands

  8x -2:55.8.0 core:backspace (input.hidden-input)
     -1:00.4.0 core:move-down (input.hidden-input)
     -0:59.9.0 autocomplete-plus:confirm (input.hidden-input)
     -0:59.9.0 snippets:expand (atom-text-editor.editor.is-focused.autocomplete-active)

Non-Core Packages

busy-signal 1.4.3 
intentions 1.1.5 
language-rust 0.4.12 
linter 2.2.0 
linter-rust 0.9.0 
linter-ui-default 1.7.1 
racer 0.20.0 
rust-api-docs-helper 0.5.1