multiple views to the same model/path will broke the editor

[gorangajic]

Describe the bug If you have multiple editors with the same file path, that are not open at the same time. During the unmount lifecycle model that is used by the other editor will be disposed, and that would break the editor.

To Reproduce

Steps to reproduce the behavior:

1. Go to https://codesandbox.io/s/bug-with-split-view-editor-z6xbyg?file=/src/App.js
2. Switch between files
3. Editor on unmount will break without any errors.