### Steps to reproduce

1. Have two WorkPackages of the same type

2. Add a required custom field for this type

3. Go to any of the WorkPackages and try to add the the other as a child via the relations tab


### What is the buggy behavior?

* Nothing happens, no error message, no children created

* When trying to do the same via an embedded table, there is at least an error message shown saying the required field can't be blank


### What is the expected behavior?

* Begin of the insertion~~AnEnd of the insertion Begin of the deletion AnEnd of the deletion error message should be Begin of the insertionshown~~

* No error message should be shown, and the relation needs to be created.End of the insertion Begin of the deletion shownEnd of the deletion


###

### Environment information

**OpenProject version**

_15.1_

**Browser**

* [x] Chrome
* [ ] Firefox
* [ ] Safari
* [ ] Mobile Safari
* [ ] Other (please specify)

**Operating System**

* [ ] Windows
* [x] Mac OS X
* [ ] Mobile iOS
* [ ] Mobile Android
* [ ] Linux (please specify distro)
* [ ] Chrome OS
* [ ] Other (please specify)

**Language**

_German_