This should work:

```javascript
if (/* the empty block */) {
  let is = Cc["@mozilla.org/io/string-input-stream;1"].createInstance(Ci.nsIStringInputStream);
  is.data = ...querySelector(...).value;
  zipWriter.addEntryStream(n, Date.now(), Ci.nsIZipWriter.COMPRESSION_FASTEST, is, !1);
}
```