Fix lighting_dirty flag bug

[lawnjelly]

In rare circumstances, changing the geometry data attached to an instance, there was the opportunity for the lighting_dirty flag to get out of sync, which could lead to access to a stale light RID, and warnings or worse.

This PR fixes the problem by ensuring the lighting is always updated on the instance when first adding GeometryData.

Fixes #41360

Conditions for bug

• On the same iteration, a light is removed, which unpairs the Light and Geometry data, and sets lighting_dirty to true
• Before the instance has the opportunity to have its lighting list updated, the GeometryData is deleted and replaced by new GeometryData. The flag defaults to false, and thus the instance lighting is never updated.
• When the instance lighting list is later hit, it reads the RID for the deleted light, and flags warnings etc.

Notes

• This was incredibly difficult to find for such a simple bug 😁 ... see the issue for details of the debugging process (a good day and half on this).

Reproduction Project

Run this project before and after the PR (click loads of times with the mouse to add the omni lights):
OmnilightBug_Cutdown4.zip

[akien-mga]

Thanks!

[akien-mga]

Cherry-picked for 3.4.1.