Resolves: fdo#78133 LibO crashes when in options dialog (Colors part)

+ Related: fdo#77934
It seems pDrDoc is always known now (related to
185c270e66d03d1f77beb8a8996393d023e818e7 ?)

Change-Id: I5f984e0e53ec49d67c07a43159433fcc26524777
Reviewed-on: https://gerrit.libreoffice.org/9219
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>