Loading of Splitview state from json adds extra div containers that break layout

[alhimik45]

Describe the bug
api.fromJSON loads state of Splitview, but also adds two empty split-view-container divs

To Reproduce
Codesandbox with reproduction. Scroll preview up and you'll find bunch of extra empty space from that unexpected divs. Duplicating api.fromJSON call leads to increased number of empty split-view-container divs

Expected behavior
Extra empty divs are not added to markup

Desktop:

• Browser Firefox
• Version 129.0.2

[alhimik45]

In 2.0.0 still same issue with extra divs with .dv-split-view-container class.

CSS workaround if anybody interested:

/* bug https://github.com/mathuo/dockview/issues/721 workaround */
.your-splitview-class > div.dv-split-view-container:not(:last-child) {
  display: none;
}

Could not be suitable if state restoration is done very often as divs still remain in DOM and can cause memory issues.