RuntimeError: Vertex shader failed to compile error in iOS

I am getting a RuntimeError: Vertex shader failed to compile in iOS.

This does not occur in desktop browsers.

The app in question can be found in: http://mgiraldo.github.io/pic/

The error log starts with:

[Cesium WebGL] Vertex shader compile log: ERROR: 0:7: ‘’ : wrong operand types no operation '’ exists that takes a left-hand operand of type ‘uniform lowp samplerCube’ and a right operand of type ‘highp 4-component vector of float’ (or there is no acceptable conversion)
ERROR: 0:7: ‘assign’ : cannot convert from ‘uniform lowp samplerCube’ to ‘Position highp 4-component vector of float’

``

Any idea why this is happening?

iOS 9

navigator.appVersion: “5.0 (Macintosh; Intel Mac OS X 10_11) AppleWebKit/601.1.46 (KHTML, like Gecko) Version/9.0 Safari/601.1.42”

This is a bug in Safari. See this thread for details: https://groups.google.com/d/msg/cesium-dev/KVS97hZLXIY/sScWEzHcAAAJ