function setEmptyTexture(gl, tex, options) {
    var target = options.target || gl.TEXTURE_2D;
    gl.bindTexture(target, tex);
    var format = options.format || gl.RGBA;
    var internalFormat = options.internalFormat || format;
    var type = options.type || gl.UNSIGNED_BYTE;
    savePackState(gl, options);
    if (target === gl.TEXTURE_CUBE_MAP) {
      for (var ii = 0; ii < 6; ++ii) {
        gl.texImage2D(gl.TEXTURE_CUBE_MAP_POSITIVE_X + ii, 0, internalFormat, options.width, options.height, 0, format, type, null);
      }
    } else if (target === gl.TEXTURE_3D) {
      gl.texImage3D(target, 0, internalFormat, options.width, options.height, options.depth, 0, format, type, null);
    } else {
      gl.texImage2D(target, 0, internalFormat, options.width, options.height, 0, format, type, null);
    }
    restorePackState(gl, options);
  }
Sets a texture with no contents of a certain size. In other words calls `gl.texImage2D` with `null`.
You must set `options.width` and `options.height`.
@param {WebGLRenderingContext} gl the WebGLRenderingContext
@param {WebGLTexture} tex the WebGLTexture to set parameters for
@param {module:twgl.TextureOptions} options A TextureOptions object with whatever parameters you want set.
@memberOf module:twgl/textures