package: avoid un-necessary modification event work.

Change-Id: Ia4b4e3edccf661b8c5f474c5c7474b5f9e497fcc
Reviewed-on: https://gerrit.libreoffice.org/7282
Reviewed-by: Fridrich Strba <fridrich@documentfoundation.org>
Tested-by: Fridrich Strba <fridrich@documentfoundation.org>