message: Fix thumbnail generation when offscreen canvas fails
diff: @@ -92,9 +92,8 @@ export async function createThumbnail(
  context.drawImage(element, 0, 0, targetWidth, targetHeight);
  let thumbnailPromise: Promise<Blob>;
  -
  - if (window.OffscreenCanvas) {
  - thumbnailPromise = (canvas as OffscreenCanvas).convertToBlob({ type: mimeType });
  + if (canvas instanceof window.OffscreenCanvas) {
  + thumbnailPromise = canvas.convertToBlob({ type: mimeType });
  } else {
  thumbnailPromise = new Promise<Blob>(resolve => (canvas as HTMLCanvasElement).toBlob(resolve, mimeType));
  }
  