[lib] Avoid setting inaccessible MessageInfo as mostRecentMessageInfo

Summary: This fixes a bug where the MessagePreview displays "No messages" even though the MessageList shows messages.

Test Plan: Flow

Reviewers: atul, subnub, palys-swm

Reviewed By: palys-swm

Subscribers: KatPo, zrebcu411, Adrian

Differential Revision: https://phabricator.ashoat.com/D810