Handle parentless nodes in nodeIsDecorated

[weswigham]

Fixes #17384

I already had a fix for this in a closed PR from a draft of our updated computed property emit, so this has even already been reviewed once 🌞

[kevinbuhmann]

Any idea when this fix will land in a release?

[weswigham]

The @next tag has had this for awhile. I believe the @insiders tag should have this fix, too. I think our next planned version release is 2.7 sometime in January, but we may do a minor release while prepping for that. In any case, it's unlikely you'll see another official versioned release until January, I think.

[alan-agius4]

If this could be in a minor release it would be even better than cutting it with the 2.7 release :)