Bug: The $convertLayoutContainerElement function of LayoutContainerNode always returns null

[1019058432]

Lexical version:0.19.0

Steps To Reproduce

1.Create a 2-column example in the editor and export it as HTML
2.Re import the exported HTML content in the editor

Link to code example:

The current behavior

The window.getComputedStyle used in this function cannot retrieve any value from the un mounted rendered HTML, so the $convertLayoutContainerElement always returns null.

The expected behavior

successfully returned column instance and rendered column node layout correctly

Impact of fix