Examples: Simplify webgl_loader_fbx

[Mugen87]

Simplified the example by just using a single mixer variable instead of an array. Notice how the following previous pattern is problematic:

for ( var i = 0; i < mixers.length; i ++ ) {

    mixers[ i ].update( clock.getDelta() );

}

If you actually have multiple mixers in your scene, clock.getDelta() will produce an invalid time delta value for the second and all subsequent mixers. It would be better to call clock.getDelta() once and reuse the same time delta value for all mixers.

[Mugen87]

https://raw.githack.com/Mugen87/three.js/dev21/examples/webgl_loader_fbx.html

[mrdoob]

Thanks!