Bounding sphere debug primitive cut in half at north pole


``` javascript
var viewer = new Cesium.Viewer('cesiumContainer');
viewer.entities.add({
position : Cesium.Cartesian3.fromDegrees(0, 90),
model : {
uri: '../../SampleData/models/CesiumAir/Cesium_Air.glb'
},
scale: 20
});
viewer.zoomTo(viewer.entities);

viewer.extend(Cesium.viewerCesiumInspectorMixin);
```

Start with the provided Cesium Viewer reproduction, especially the entity positioned at latitude 90 and the viewerCesiumInspectorMixin debug view. Trace how the bounding sphere debug primitive is displayed at the north pole and compare it with positions away from the pole. Done means the complete bounding sphere is visible rather than cut in half.

Written by the indexing model from the issue text.