halfwidth needs let not const

[NikLever]

initializeLocalHeadGeometry (localHeadWidth, localHeadGeometry) {
        this.localHeadGeometry = [];
        if (!localHeadGeometry) {
            const halfWidth = localHeadWidth || 1.0;
            halfWidth = halfWidth / 2.0;

halfWidth should be declared as let to enable it to be divided by 2.

[mkkellogg]

Thanks for noticing this! I've pushed a change that should fix it.