Nodes that VE does not recognize are initialized into ve.ce.MWAlienNode and are focusable. However, similarly to what we had with empty/hidden transclusions, some of the alien nodes are empty, which makes them dimensionless and impossible for the user to interact with (even only to delete/move)
Alien nodes should have a minimum width/height in case they are empty.
We've done this before to MWTransclusionNode, see this patchset:
- https://gerrit.wikimedia.org/r/#/c/193975 (original fix)
- https://gerrit.wikimedia.org/r/#/c/195313/ (followup)