refac

Co-Authored-By: Johannes Fahrenkrug <16358+jfahrenkrug@users.noreply.github.com>

backend/open_webui/routers/retrieval.py

@@ -1971,6 +1971,7 @@ async def process_web(
                     docs,
                     collection_name,
                     overwrite=overwrite,
+                    add=(not overwrite),
                     user=user,
                 )
             else: