Deleted submission still have a title attribute with speaker and title

[zivillian]

Current Behavior

Deleting a submission, after publishing the schedule results in a schedule with the talk title and speaker removed and only square brackets, but the title attribute still contains the speaker and title (and is shown on hover).

Expected Behavior

The Speaker and talk title is no longer shown as a tooltip in the schedule.

Steps to Reproduce

1. publish the schedule
2. delete a submission
3. open public schedule
4. speaker and title is still visible when hovering

Context

I was just playing with pretalx.

Your Environment

• Version used: installed on 2019-12-02 via https://docs.pretalx.org/administrator/installation.html
• Environment name and version (e.g. Chrome 39, python 3.5): Chrome 78.0.3904.108, python 3.7
• Operating System and version (desktop or mobile): debian 10, windows 10