Error using setSheenColorFactor in Material

[chesstrian]

Hi,

The issue is reproducible from model-viewer version 3.2.0 to 4.1.0:

const viewer = document.getElementsByTagName('model-viewer')[0]
viewer.model.materials[0].setSheenColorFactor('#ffffff')

Output:

Uncaught TypeError: Cannot read properties of undefined (reading 'set')