Fix memory leaks for some SwXMLTextBlocks

... which should be freed even if GetError() != 0

Change-Id: Ifbf72aa17f8bcbdcc3b1504a105aa32e94397ee3
Reviewed-on: https://gerrit.libreoffice.org/9807
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>