Update upload.go

upload/upload.go

@@ -502,6 +502,9 @@ func pdfThumbnail(objectPath string, file *zip.File, bucket *oss.Bucket) ([]inte
 		return nil, errors.New("image ext is not found")
 	}
 
+    if img == nil {
+        return nil,  errors.New("image is decode fail")
+    }
 	//if err = webp.Encode(buf, img, &webp.Options{Lossless: true}); err != nil {
 	//	return nil, err
 	//}