SwCursor::MovePara() may move the uno cursor past the end of the
selection range, check for this explicitly.

In practice this makes sure that in case a 1-paragraph cell text is
selected, we never jump to the next cell for a selection created from
the previous cell.

Change-Id: Ibe2d00cfa75ed0c32b9c89d86cfae3b51d70ddc6
Reviewed-on: https://gerrit.libreoffice.org/64509Reviewed-by: Miklos Vajna <vmiklos@collabora.com>
Tested-by: Jenkins