Swarm: Compat with Non-Swarm clients, messages kept?

Scenario

• Alice (client-qt, swarm) adds Bob (non-swarm client)
• Alice will create a swarm that should be shown
• Bob accepts the invite
• Because Bob is a non-swarm compatible member, the swarm is deleted, but contact still present

Current result

When conversation is removed, old messages are still there.

Expected

Messages from swarm should be deleted