As a user, when using the Export XLSX (Current Fields) and the issues have Sub-Tasks, the column Sub-Tasks is empty

As a user, when using the Export XLSX (Current Fields) option and the issues have Sub-Tasks to be exported, the column Sub-Tasks is empty on the xlsx file.

Steps to reproduce

Step	Result
Go to the Issue Navigator and use a JQL to show issues with sub-tasks
XLSX result (Sub-tasks column)