Switching syntax in source mode wrongly joins the realtime session

Steps to reproduce:

1. Go to the administration, in Editing -> Syntax uncheck "xwiki/2.0" under disabled syntaxes
2. Create a new page
3. Go to source mode
4. Type some content like "test"
5. Select another syntax like "XWiki 2.0" in the syntax selection
6. Select "Yes" when asked if the content shall be converted.
7. Disable source mode

Expected result:

After the syntax conversion, the saving toolbar stays the same. After the last step, only a single "Done" button is displayed.

Actual result:

After the syntax conversion, a message that the realtime session is joined is displayed. After the disabling the source mode, the saving toolbar is displayed twice.

I've attached a screen recording that shows the reproduction steps.