JS scroll error

[convcha]

https://qiita.com/nishihara_zari/items/9b074e38f4242506472f
https://qiita.com/msekino/items/e4b9839de4ff5fb56930

tui-editor-extScrollSync.js:635 Uncaught TypeError: Cannot read property 'sectionRatio' of undefined
    at ScrollManager._getScrollTopForMarkdown (tui-editor-extScrollSync.js:635)
    at ScrollManager.syncMarkdownScrollTopToPreview (tui-editor-extScrollSync.js:700)
    at tui-editor-extScrollSync.js:296
    at tui-editor-Editor.js:3033
    at forEachArray (tui-code-snippet.js:947)
    at Object.forEach (tui-code-snippet.js:1024)
    at EventManager.emit (tui-editor-Editor.js:3032)
    at HTMLDivElement.<anonymous> (tui-editor-Editor.js:2744)
    at HTMLDivElement.dispatch (jquery.js:5236)
    at HTMLDivElement.elemData.handle (jquery.js:5043)
_getScrollTopForMarkdown @ tui-editor-extScrollSync.js:635
syncMarkdownScrollTopToPreview @ tui-editor-extScrollSync.js:700
(anonymous) @ tui-editor-extScrollSync.js:296
(anonymous) @ tui-editor-Editor.js:3033
forEachArray @ tui-code-snippet.js:947
forEach @ tui-code-snippet.js:1024
emit @ tui-editor-Editor.js:3032
(anonymous) @ tui-editor-Editor.js:2744
dispatch @ jquery.js:5236
elemData.handle @ jquery.js:5043