message: missingThumbnails never can be null. It is not needed to delete it.
diff: @@ -164,10 +164,6 @@ export class ContentWrapper {
  }
  }
  - if (m.missingThumbnails === 0) {
  - delete m.missingThumbnails;
  - }
  -
  if (MediaDTOUtils.isPhoto(m)) {
  delete (m as VideoDTO).metadata.bitRate;
  delete (m as VideoDTO).metadata.duration;
  