Error thrown when creating second style

[Reinmar]

I got the error while typing this text:

[szymonkups]

I took a while to debug this. It looks like it will be a renderer issue.
When first style is applied, view looks something like this:

<p>You can <strong>bold</strong>[]</p>

And inline filler is applied in the second text node (after </strong>).
When second attribute is applied:

<p>You can <strong>bold</strong> or <em>italicise</em></p>

Rendering occurs. At the begining, rendering checks if selection is in inline filler: https://github.com/ckeditor/ckeditor5-engine/blob/ceb51fa/src/view/renderer.js#L183

Renderer._isSelectionInInlineFiller is trying to translate view selection position into DOM position, (by using DomConverter.viewPositionToDom), but this is impossible because:

• in the view we've already changed *italicize* to <em>italicize</em>,
• there is no DOM corresponding element as it will be created later on during this rendering.

[Reinmar]

There's a chance that this issue will be fixed in ckeditor/ckeditor5-engine#676.

[Reinmar]

Fixed by ckeditor/ckeditor5-engine#676.