Uncaught TypeError: Cannot read property 'buffer' of undefined

Uncaught TypeError: Cannot read property 'buffer' of undefined

**Atom Version**: 0.161.0-f866e69
**System**: linux 3.16.0-28-generic
**Thrown From**: [atom-color-highlight](https://github.com/abe33/atom-color-highlight) package, v2.0.16
### Steps To Reproduce
1. Change font size.
### Stack Trace

```
At ~/.atom/packages/atom-color-highlight/lib/dot-marker-view.coffee:16

TypeError: Cannot read property 'buffer' of undefined
at new DotMarkerView (~/.atom/packages/atom-color-highlight/lib/dot-marker-view.coffee:16:22)
at AtomColorHighlightView.module.exports.AtomColorHighlightView.rebuildMarkers (~/.atom/packages/atom-color-highlight/lib/atom-color-highlight-view.coffee:150:26)
at ~/.atom/packages/atom-color-highlight/lib/atom-color-highlight-view.coffee:1:1
at /opt/atom/share/atom/resources/app/src/config.js:571:20
at Emitter.module.exports.Emitter.emit (/opt/atom/share/atom/resources/app/node_modules/event-kit/lib/emitter.js:82:11)
at Config.module.exports.Config.setRawValue (/opt/atom/share/atom/resources/app/src/config.js:556:29)
at Config.module.exports.Config.set (/opt/atom/share/atom/resources/app/src/config.js:189:14)
at SettingsPanel.module.exports.SettingsPanel.set (/opt/atom/share/atom/resources/app/node_modules/settings-view/lib/settings-panel.js:156:28)
at /opt/atom/share/atom/resources/app/node_modules/settings-view/lib/settings-panel.js:201:26
at TextBuffer.module.exports.Emitter.emit (/opt/atom/share/atom/resources/app/node_modules/emissary/lib/emitter.js:118:15)
at /opt/atom/share/atom/resources/app/node_modules/text-buffer/lib/text-buffer.js:1143:17

```

/cc @atom/core

錯誤發生在 lib/dot-marker-view.coffee 的第 16 行，此處存取了未定義物件上的屬性 'buffer'。首先檢查 DotMarkerView 建構函式，確認缺少哪個參數。檢查 lib/atom-color-highlight-view.coffee 中的 rebuildMarkers 如何建立檢視。在安裝了該套件的情況下變更 Atom 中的字型大小來重現問題，然後追蹤流程，確保 marker 具有有效的 editor 或 buffer 參照。

由索引模型根據 Issue 內容生成。