fdo#73300: sw: don't swap in all images when loading files

(regression from bd55f05b332c1573bd410fd9e21ea7fcf977e1b0)

Change-Id: I55532ac0fe983461e961a61149479343d2b879a1
(cherry picked from commit 9b9eb2e4f619c63eabdc54b5d749ac55d8eaf333)
Reviewed-on: https://gerrit.libreoffice.org/7809
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>