Unable to export Test Steps User Picker fields with Document Generator

Description
Document Generator cannot export the User Picker field type from Test Step custom fields.

How to reproduce

1. Go to Test Step custom fields
2. Create a new User Picker type field
   
3. Go to a Manual Test and create Steps
4. Add a value to the new User Picker field
   
5. Export it using Document Generator
   Template used for testing -> userpickerteststepfield.docx

Actual result/Attachments
It doesn´t export the User Picker field infromation

Expected result
It should export the User Picker field information