Vertical sort is broken on Firefox 134

[cyril-sf]

Describe the bug
When trying to reorder items in a vertical collection on Firefox 134, the selected item remains at its original position once dropped

To Reproduce
Steps to reproduce the behavior:

1. Go to the Ember Sortable Demo with Firefox 134
2. Try to reorder the Zero item between Two and Three
3. See error

Expected behavior
Zero can be positioned between Two and Three

Screenshots

Notice how there is no space to drop the selected item

Additional context
We tracked down the root cause and it's linked to a change of behavior in Firefox 134. We opened an issue in Bugzilla

getComputedStyle returns a single length when horizontal and vertical have the same value on Firefox 134, no any other browser or older Firefox version. Because of this, getBorderSpacing (addon/src/utils/css-calculation.ts) returns undefined as vertical value. The height of a sortable item ends up being NaN.

We have a fix available if you're interested yapplabs@c4e04e9