Crash in RenderingContext.CopyTo

[craigfowler]

The class RenderingContext has a crash bug in its CopyTo method, due to a copy-paste error. The copy of METAL definitions accidentally makes use of the TAL dictionary.

var talDefinitions = TalModel.GetAllDefinitions();
var metalDefinitions = MetalModel.GetAllDefinitions();

foreach(var key in talDefinitions.Keys)
{
  container.TalModel.AddLocal(key, talDefinitions[key]);
}

foreach(var key in metalDefinitions.Keys)
{
  // Here is the error - that should be metalDefinitions below, not talDefinitions
  container.MetalModel.AddLocal(key, talDefinitions[key]);
}

This can cause it to crash with KeyNotFoundException in the dictionary access.