Missing texture on a single Decal causes clustering artifacts to appear on other decals

Tested versions

4.3dev4

System information

Godot v4.3.dev4 - Debian GNU/Linux trixie/sid trixie - Wayland - Vulkan (Forward+) - dedicated AMD Radeon RX 5600 XT (RADV NAVI10) () - AMD Ryzen 5 2600X Six-Core Processor (12 Threads)

Issue description

When a decal has a missing texture, other decals affecting the same mesh (or maybe all other decals? -- I only have one mesh so I haven't tested thoroughly) flicker. Sometimes they are rendered correctly. Other times, they are only partly rendered.

I'm using the forward_plus rendered -- this does not seem to be a result of the 7-decal limit for the mobile renderer, and it works fine when I replace the missing texture.

Steps to reproduce

I noticed this when I forgot to create one of my decal textures, and suddenly the rendering was wrong.

In the MRP, you can use the mouse to spin the shape. When you do, you'll notice that the decals flicker.

If you replace temp-26.png (just copy any of the other ones), the flicker goes away entirely.

Minimal reproduction project (MRP)

flicker.zip

Start by running the attached flicker.zip minimal reproduction in Godot 4.3dev4 with the Forward+ renderer, then rotate the shape and observe decals while temp-26.png is missing. Compare this with the same project after replacing temp-26.png with another decal texture; done means the missing texture no longer causes other decals to flicker or render only partially.