message: Prevent reading while dropping a catalog entry
diff: @@ -274,6 +274,7 @@ bool CatalogSet::DropEntry(ClientContext &context, const string &name, bool casc
  throw CatalogException("Cannot drop entry \"%s\" because it is an internal system entry", entry->name);
  }
  + lock_guard<mutex> read_lock(catalog_lock);
  DropEntryInternal(context, entry_index, *entry, cascade);
  return true;
  }
  