When removing a template from a document type I get a bad request error and the template is not removed

[andr317c]

Which Umbraco version are you using? (Please write the exact version, example: 10.1.0)

15.0.0-rc4

Bug summary

I am unable to remove an Allowed Template from a document type

remove

Specifics

No response

Steps to reproduce

1. Create a DocumentType with a template
2. Try to remove template

Expected result / actual result

I would expect that I was able to remove the template

[bergmania]

Error seems to be because the payload is wrong:

{
...
   "defaultTemplate": {
      "id": ""
   }
...
}

instead of the expected

{
...
   "defaultTemplate": null
...
}

[madsrasmussen]

Fixed by #17516