Fix: prevent crash when calling BufferGeometry.setFromPoints with too few points

[rotu]

Description

#29696 introduced a crash condition where calling BufferGeometry.setFromPoints would cause a crash like three.module.js:10894 Uncaught TypeError: Cannot read properties of undefined (reading 'x') if trying to set fewer points than is in the position attribute.

[rotu]

It may be appropriate to also emit a warning or to also set the draw range to only the newly set positions.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	339.14 78.99	339.14 78.99	+0 B +0 B
WebGPU	483.15 134.15	483.15 134.15	+0 B +0 B
WebGPU Nodes	482.62 134.06	482.62 134.06	+0 B +0 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	464.59 111.96	464.62 111.98	+25 B +17 B
WebGPU	552.25 149.49	552.28 149.51	+25 B +17 B
WebGPU Nodes	508.13 139.2	508.16 139.22	+25 B +17 B

[Mugen87]

It may be appropriate to also emit a warning or to also set the draw range to only the newly set positions.

If the developer intentionally wants to update just a part of the position buffer but rendering the entire range, updating draw range or emitting a warning would be confusing though. I think the PR is fine as it is.