fdo#72260: guard against duplicate "name" attribute

Change-Id: I1ee4b82e04318a50db8bb54bd5c7e00c79177d37
Reviewed-on: https://gerrit.libreoffice.org/6984
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>