Scene.dispose(), 'LEQUAL' undefined

Hi,

I'm getting a crash in the current Babylon 2.4 Beta on Scene.Dispose():

"Unable to get property 'LEQUAL' of undefined or null reference"
at Engine.prototype.setDepthFunctionToLessOrEqual
at Engine.prototype.wipeCaches

Looks to be due to the addition of "this.setDepthFunctionToLessOrEqual();" to wipeCaches(), this references this._gl which is already null at this point.