code: function destroyTextures () {
      for (var i = 0; i < numTexUnits; ++i) {
        gl.activeTexture(GL_TEXTURE0 + i)
        gl.bindTexture(GL_TEXTURE_2D, null)
        textureUnits[i] = null
      }
      values(textureSet).forEach(destroy)
  
      stats.cubeCount = 0
      stats.textureCount = 0
    }
docs: Called when regl is destroyed