gLTF Model Load accessing undefined material

[Digicrat]

I've pulled the latest changes in the Cesium GLTF branch, and also updated/re-compiled the Collada2gltf converter.

I am once again trying to convert a model from the NASA website (http://www.nasa.gov/multimedia/3d_resources/assets/eoss-messenger.html). This time the converter appears to be functioning, but I am getting JS errors when I attempt to load the model using the CesiumViewer2 example.

The error is on line 1169 of Model.js. primitive.material is defined as "", and there is no corresponding blank name in the materials array. As a result we get the exception of accessing instanceTechnique from an undefined property.

I'm not familiar enough with this code to know if this is a bug in Cesium or a problem in the converter (paired with a lack of error handling in Cesium).

[pjcozzi]

Thanks for the issue. Glad you are checking out glTF.

This is most likely a bug in the converter. Perhaps #194. CC @fabrobinet