Unread counter increased while in in chat

[FelberMartin]

Describe the bug

When a user is in a chat and receives a new message and then navigates back to the conversation overview screen, the unread messages indicator is shown for this new message, even though the user has just read this message in the chat.

To Reproduce
Steps to reproduce the behavior:

1. Go to any chat with no unread messages
2. In the same chat, write a message with another user from a different client (eg the web app)
3. In the android app, receive the new message
4. Navigate back and see in the ConversationOverview that the unread counter is increased for this chat

Expected behavior
The unread counter should not increase