[fix] autocompleter error handling

    # check if search query is set

    if not query.getSearchQuery():

        return

        return '', 400

    # run autocompleter

    completer = autocomplete_backends.get(request.cookies.get('autocomplete'))

    # check if valid autocompleter is selected

    if not completer:

        return

        return '', 400

    # run autocompletion

    raw_results = completer(query.getSearchQuery())