message: fix typeof check
diff: @@ -169,7 +169,7 @@ export function getAttachment(gl: GLRenderingContext, extensions: WebGLExtension
  }
  function isImage(x: TextureImage<any> | TextureVolume<any> | HTMLImageElement): x is HTMLImageElement {
  - return typeof HTMLImageElement !== undefined && (x instanceof HTMLImageElement);
  + return typeof HTMLImageElement !== 'undefined' && (x instanceof HTMLImageElement);
  }
  function isTexture2d(x: TextureImage<any> | TextureVolume<any>, target: number, gl: GLRenderingContext): x is TextureImage<any> {
  