gtk listens to the selection so realizes that the GtkEntry selection
is not the desktop selection anymore and drops the visual selection.

But we're relying on the visual selection to know what part of
a multiselection we are modifying

Change-Id: I42d5718ba029b4f94c436cb755485d05511b5708
Reviewed-on: https://gerrit.libreoffice.org/71576
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>