we only support simple labels in the InternalDataProvider, bnc#864396

Change-Id: Ie31c5c73bb5185125fd4493c4e476997e2e9bc63
Reviewed-on: https://gerrit.libreoffice.org/8190
Reviewed-by: Andras Timar <andras.timar@collabora.com>
Tested-by: Andras Timar <andras.timar@collabora.com>