MM: fix workaround for single paragraph docs

There is already a workaround for pasting a document with a single
paragraph by appending a dummy empty paragraph to the working copy.

This patch removes the dummy paragraph from the target document.

Change-Id: I288d35264bf6f1a5f92c50d6a309e3bdd4ab5836
Reviewed-on: https://gerrit.libreoffice.org/10964
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>