26.3.beta.1 - WorldScape3D - Undoing addition of node breaks viewport interaction #1388

Tested versions

Tested in 26.3.beta.1. Reproducible in both standard and Mono versions.
Versions below 26.3.beta.1 are inapplicable.

System information

MacOS Sonoma 14.2.1 - Apple Silicon M1

Issue description

I first encountered this issue by accidentally adding a WorldScape3D node when I intended to add a WorldEnvironment. I cancelled the "Select the terrain data directory" prompt and undid the addition of the node with ⌘Z. Immediately upon doing so, I was unable to interact with any nodes or gizmos within the viewport. The Scene hierarchy and Inspector were unaffected; only the viewport.

Upon undoing the addition of the WorldScape3D node and sometimes when clicking anywhere in the viewport, this error is generated:

ERROR: modules/worldscape_3d/logger.h:62 - WorldScape3D#0541:get_intersection:720: Invalid mouse camera

Also, this error repeatedly occurs whenever the mouse moves across the world axes and gizmos:

ERROR: Unable to convert array index 0 from "Nil" to "Vector2i".

After further testing, I discovered that it doesn't matter whether you cancel the "Select the terrain data folder" prompt or fulfill it; undoing the addition of the WorldScape3D node causes this issue either way.

I first encountered this in the Mono version, but was also able to reproduce it in the standard version, even experiencing crashes in both versions.

Restarting the editor fixes the issue, but it can be reproduced again.

Steps to reproduce

1. Create and open a new project.
2. Add any 3D node or click the shortcut to create a new "3D Scene".
3. Add a WorldScape3D node, then continue past the "Select the terrain data folder" prompt by either cancelling or fulfilling it.
4. Press Undo to remove the WorldScape3D node. Now observe broken viewport interaction.

Minimal reproduction project (MRP)

Can easily be reproduced from a newly-created project file.