this is a safe backportable fix, the unconditional

nFlags |= SelectionEngineFlags::CMDEVT

looks the real dubious thing to me, but only the gtk3 backend has swipe support
so just returning immediately on a swipe definitely ok

Change-Id: Iade26d0d9260ce76dfb2766ac9e5ca9fa9275bf4
Reviewed-on: https://gerrit.libreoffice.org/48528Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Eike Rathke <erack@redhat.com>