message: support cif files with only safeFrames
diff: @@ -635,7 +635,7 @@ async function parseInternal(data: string, runtimeCtx: RuntimeContext) {
  return error(tokenizer.lineNumber, `Unfinished save frame (${saveFrame.header}).`);
  }
  - if (blockCtx.categoryNames.length > 0) {
  + if (blockCtx.categoryNames.length > 0 || saveFrames.length > 0) {
  dataBlocks.push(Data.CifBlock(blockCtx.categoryNames, blockCtx.categories, blockHeader, saveFrames));
  }
  