Single/current message can be collapsed in thread view

[ChristophWurst]

Steps to reproduce

1. Open a single message thread
2. Click on the header of the message (sender/subject)

Expected behavior

Nothing happens

Actual behavior

The message collapses.

This is fine for other messages in a thread, but for the only/current message this shouldn't even be offered.

Mail app version

2.0.0 beta 3

Mailserver or service

No response

Operating system

No response

PHP engine version

No response

Web server

No response

Database

No response

Additional info

No response