Sampler: Don't set _texture to null.

[Mugen87]

Fixed #31747.

Description

#31497 introduced the private _texture property in Sampler to fix #31480. This property is set to null if a texture dispose happens.

However, a lot of code in context of bind groups breaks if the texture property of a sampler binding is null. #31747 is one example how runtime errors occur, in this instance during the init of a bind group. However, the same error occurs when the WebGPU backend tries to create bind group layouts. All this code assumes binding.texture never points to null. Even if a texture is disposed, the (cached) binding must point to it for the case the texture is reused again.

The cached bindings I'm talking about are the bindings from the render object:

three.js/src/renderers/common/Bindings.js

Line 80 in 47c6359

const bindings = renderObject.getBindings();

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	338.24 79.14	338.24 79.14	+0 B +0 B
WebGPU	580.27 160.28	580.3 160.29	+33 B +8 B
WebGPU Nodes	578.88 160.04	578.91 160.05	+33 B +7 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

	Before	After	Diff
WebGL	469.88 113.85	469.88 113.85	+0 B +0 B
WebGPU	649.98 175.93	650.01 175.94	+33 B +8 B
WebGPU Nodes	604.09 165.11	604.12 165.11	+33 B +8 B