Resolves: rhbz#1146169 a11y frames label dies before frame

Change-Id: I2bc45dcb92b8e68bf4ae4df72c0fbd4e3b535604
Reviewed-on: https://gerrit.libreoffice.org/12142
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Miklos Vajna <vmiklos@collabora.co.uk>