Close pipes on file writer error (#21900)

app/file.go

@@ -824,6 +824,7 @@ func (t *UploadFileTask) postprocessImage(file io.Reader) {
 		_, aerr := t.writeFile(r, path)
 		if aerr != nil {
 			mlog.Error("Unable to upload", mlog.String("path", path), mlog.Err(aerr))
+			r.CloseWithError(aerr) // always returns nil
 			return
 		}
 	}

app/upload.go

@@ -93,6 +93,7 @@ func (a *App) runPluginsHook(c request.CTX, info *model.FileInfo, file io.Reader
 		if fileErr := a.RemoveFile(tmpPath); fileErr != nil {
 			mlog.Warn("Failed to remove file", mlog.Err(fileErr))
 		}
+		r.CloseWithError(err) // always returns nil
 		return err
 	}