Fix equality check for null corpus

app/api/api_v1/routers/search.py

@@ -185,7 +185,7 @@ def search_documents(
     token.decode_and_validate(db, request, app_token)
 
     # If the search request IDs are null, we want to search using the app token corpora.
-    if search_body.corpus_import_ids is None:
+    if search_body.corpus_import_ids == [] or search_body.corpus_import_ids is None:
         search_body.corpus_import_ids = cast(Sequence, token.allowed_corpora_ids)
 
     # For the second validation, search request corpora Ids are validated against the