fix: ignore new messages from channels a user is not a member in message.new handler for ChannelList

[MartinCupela]

🎯 Goal

When a user is removed from a channel with channel.removeMembers([targetId],{text:"bye"}):

1. Remove the channel from the channel list - and keep it removed
2. Remove the channel from the active channel - thus prevent user from being able to send messages
3. (Optional) Set a new active channel to undefined | ???