mono/MonoGame — pull request #3332 by mgarstenauer (2014-12-29 18:45:11+00:00)
Title: Fix for MeshHelper.CalculateNormals

`MeshHelper.CalculateNormals` fails if the "Normal" channel does not already exist. The reason is that `VerexChannelCollection.Get(string)` throws an `ArgumentException` if the channel is missing. It does not return null as expected.