When I select NULL as the value and click update, it shows that the update is successful, but when I refresh it changes back to add-avatar. It seems that all fields cannot be changed to null.
TL;DR
Developers are unable to update values to null in appwrite. Despite selecting NULL and clicking update successfully, the value reverts back to 'add-avatar' on refresh. This issue indicates that all fields cannot be changed to null in appwrite.