This was a problem since commit 29d4ecf3
(tdf#115574 sot: fix Excel -> Writer paste, 2018-03-29), the root cause
seems to be that (older?) Safari provides RTF clipboard content which
simply doesn't contain the images.

Just to back to the old behavior on macOS for now, hopefully the
problematic RTF producer will go away in the long run.

Change-Id: I5c40b28671978cfbf8593f1cc9775985dffc5030
Reviewed-on: https://gerrit.libreoffice.org/60641Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins