Setting Extra Spacing on a FontVariation with a bitmap font causes missing character symbols to appear

[NewDefectus]

Godot version

4.2.dev4

System information

Godot v4.2.dev4 - Windows 10.0.19045 - Vulkan (Forward+) - dedicated NVIDIA GeForce GTX 1050 Ti (NVIDIA; 31.0.15.3623) - Intel(R) Core(TM) i7-8700 CPU @ 3.20GHz (12 Threads)

Issue description

I have a scene in my game where I need some special spacing on a font. The font happens to be a bitmap font (it has to be in my case, to avoid rendering issues), which on its own renders fine:

However (and I believe this is new since 4.2.dev4, as I didn't see it happen in 4.2.dev3), setting any of the Extra Spacing settings causes the font to error and produce missing symbols:

Steps to reproduce

Run the minimal reproduction project, and try setting/unsetting the Extra Spacing options (the font only renders when they are all set to 0)

Minimal reproduction project

FontVariationBug.zip

[matheusmdx]

Bisecting shows that started after #80954