Using last visible message ignores an edge case:
If we are on top of the list (i.e oldest message), any received message
should be appended (it must be visible).
When using last-visible message for this, a newer message will have <
clock-value, therefore it will be offloaded to the database, which is
not correct.
Instead if we use the first-not-visible message, this should not be a
problem. If we are on top of the list, this will be nil, and therefore
the message will be appended.
Signed-off-by: Andrey Shovkoplyas <motor4ik@gmail.com>
Andrea Maria Piana
c2e195979c