Bug when switching from 2D view to columbus view

When you run this example in SandCastle, repeatedly switching from 2D view to columbus view, will appear error:

An error occurred while rendering. Rendering has stopped.

RangeError: Invalid array length

In Chrome Browser,v32.0.1700.107 m

Thanks. I can repeat this and have submitted https://github.com/AnalyticalGraphicsInc/cesium/issues/1518.