Writer: Fix empty selection callback.HEADmaster

Issue: When selecting words using CTRL+Mouse click, core side needs to send the selection rectangles to Online side.
Rectangles are not sent but an empty message.

Fix: Aggregate selection rectangles from all cursors in the ring.
In add mode (CTRL+click multi-selection), the actual selections
are stored in ring cursors, while m_pCurrentCursor may be empty.
Without aggregation, callback only reads from m_pCurrentCursor and sends an empty payload,
clearing the selection on the online side.

Change-Id: I9af5d850ab59644f56358a9ecc5985b2ad529619
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/201841
Tested-by: Jenkins
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>

0 files changed, 0 insertions, 0 deletions