Removed invalid call to GL.enable(). GL.DEPTH_STENCIL represents a pixel data format, not something that can be enabled.
Fixed getUniformLocationNameFromAgalRegisterIndex().
Update setGLSLTextureAt() not to crash if texture is null, and instead to unbind the current texture.
Updated setGLSLVertexBufferAt() not to crash if buffer is null, and instead to unbind the current buffer.