PointLight.setRadius(POSITIVE_INFINITY) silently breaks the engine

[riccardobl]

Setting PointLight radius to POSITIVE_INFINITY as done in the gltf loader

https://github.com/jMonkeyEngine/jmonkeyengine/blob/master/jme3-plugins/src/gltf/java/com/jme3/scene/plugins/gltf/LightsPunctualExtensionLoader.java#L130

causes unexpected behavior across the engine by causing some values to become NaN.