[EM] Fix for Zotero 4.0.24
As of https://github.com/zotero/zotero/commit/0cd183613f5dacc85676109c3a5c6930e3632fae globals do not seem to be isolated to individual translators, so RDF object, importantly the "itemDone" handler, can get overridden by other translators, which means we cannot reuse the RDF object from detectWeb