Summernote: Image resize handle still show after changing to code mode.

[hackerwins]

steps to reproduce

1. Insert a image
2. Select image with mouse
3. Click the code view button on toolbar.

browser version and os version

Chrome Version 60.0.3112.90 (Official Build) (64-bit)

screenshot of issue

[hackerwins]

This can be fixed with handling summernote.codeview.toggled event.
https://github.com/summernote/summernote/blob/develop/src/js/base/module/Placeholder.js#L11

[youjungeee]

이거 하고 계신 분 없나요?
그렇다면 제가 도전해보겠습니다~ ^^

[hackerwins]

@cocopang Thanks for contribution.