Fix geometry entity with dynamic color

[hpinkos]

• Fixes dynamic color when the result parameter is not used
• Fixes dynamic depth fail color

var viewer = new Cesium.Viewer('cesiumContainer');
viewer.scene.globe.depthTestAgainstTerrain = true;

var lineColor = Cesium.Color.RED;
var depthColor = Cesium.Color.BLUE;

var redLine = viewer.entities.add({
    polyline : {
        positions : Cesium.Cartesian3.fromDegreesArray([-75, 35,
                                                        -125, 35]),
        width : 5,
        followSurface : false,
        material : new Cesium.ColorMaterialProperty(new Cesium.CallbackProperty(function() {
                        return lineColor;
                    }, false)),
        depthFailMaterial : new Cesium.ColorMaterialProperty(new Cesium.CallbackProperty(function() {
                        return depthColor;
                    }, false))
    }
});

Sandcastle.addToolbarButton('Button', function() {
    lineColor = Cesium.Color.ORANGE;
    depthColor = Cesium.Color.PURPLE;
});

viewer.zoomTo(viewer.entities);

[cesium-concierge]

@hpinkos, thanks for the pull request! Maintainers, we have a signed CLA from @hpinkos, so you can review this at any time.

⚠️ I noticed that CHANGES.md has not been updated. If this change updates the public API in any way, fixes a bug, or makes any non-trivial update, please add a bullet point to CHANGES.md and comment on this pull request so we know it was updated. For more info, see the Pull Request Guidelines.

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[hpinkos]

This is a perfect example for why I think we should always prefer

var result = someFunction(resultParameter)
// do more things with result

instead of

someFunction(resultParameter);
//do more things with resultParameter

I think it makes the code easier to follow for someone who is not used to how we use result parameters, and it avoids mistakes like this where the result parameter might not actually be used.

[mramato]

I agree with you. I think this is in our coding guide, can you check and open a PR if not? Thanks.

[mramato]

Does this fix #5371?

[hpinkos]

Does this fix #5371?

Nope

[hpinkos]

@ggetz can you review?

[mramato]

I have a feeling there are quite a few random bugs that this will fix, whether we know it now or not.