When a version is deleted from the project, issues that used to be on this version do have fixVersion set to None, but the issue history does not display any entries related to this.

It is a problem when users want to filter issues without versions on Agile boards. Issues that used to be on a version that has been deleted do not show up when we filter by Issues without version.

Steps to reproduce:

1. create an Agile project
2. create an issue on this project
3. create a version on this project
4. add this version to the fixVersion field of the issue
5. delete the version
6. go to the Agile board, expand Versions tab and click on Issues without versions

Expected Behaviour:

the issue should be displayed on the Backlog

Actual Behaviour:

the issue is NOT displayed on the Backlog