fix: npe in depth shader diffuseTexture

[dar-dev]

Line: https://github.com/libgdx/libgdx/blob/7fb396541a8c2777c92a5062aaa49afcab0bec1f/gdx/src/com/badlogic/gdx/graphics/g3d/shaders/DefaultShader.java#L237C32-L237C50

This is throwing an npe because the DepthShader canRender() is recycling the shader without the diffuse texture attribute.

Step to replicate:

• open: "gdx-gltf-demo-desktop-2.1.0.jar" from gdx-gltf repo (https://github.com/mgsx-dev/gdx-gltf)
• load this glTF model: https://sketchfab.com/3d-models/2021-lamborghini-countach-lpi-800-4-d76b94884432422b966d1a7f8815afb5
• enable shadow pass from gltf scene manager
• npe

[mgsx-dev]

It fixes the issue you have but it introduces a regression : let say you have 2 models without blending, one with a diffuse texture and another one without diffuse texture, 2 shaders will be generated instead of one. And will then produce some unnecessary shader switches when rendering.

[dar-dev]

It fixes the issue you have but it introduces a regression : let say you have 2 models without blending, one with a diffuse texture and another one without diffuse texture, 2 shaders will be generated instead of one. And will then produce some unnecessary shader switches when rendering.

If we use the same shader an npe is thrown, so.. it never worked (at least in our tests).
How can we avoid this shader switch ? Do we need to introduce an npe check in diffuseTexture local setter ?

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