skip lookup with full names when there are none

nominatim/api/search/db_search_builder.py

@@ -223,6 +223,7 @@ class SearchBuilder:
 
         # Partial term to frequent. Try looking up by rare full names first.
         name_fulls = self.query.get_tokens(name, TokenType.WORD)
+        if name_fulls:
             fulls_count = sum(t.count for t in name_fulls)
             # At this point drop unindexed partials from the address.
             # This might yield wrong results, nothing we can do about that.