### Steps to reproduce

1. Create multiple work packages with any two or more interleaved types

2. Create custom field with format boolean

3. Enable it for one of the used types

4. Set value of the custom field for two packages to true and false, but don't touch other work packages

5. Go to work packages list

6. Show the custom field column and group by it


### What is the buggy behaviour?

* Depending on order of created work packages, groups with the work packages will visually (not from the number of items in the group) contain work packages that don't have custom field set

* Again depending on the order, work packages that didn't have custom field value set will be in additional groups interleaved with groups of work packages of other types


### What is the expected behaviour?

1. There should be only three groups, for true, false and absent values

2. It should be decided what happens with work packages without value set, possible ways:

1. They should be grouped by default value together with work packages for which value was explicitly set

2. They should be grouped in additional group with default value

3. They should not show default value and be grouped with work packages having absent value


### Important note

Problem is caused by difference between Begin of the insertionapi that returnsEnd of the insertion Begin of the deletion api/frontend gettingEnd of the deletion default value for work packages Begin of the insertionthat don't haveEnd of the insertion Begin of the deletion withoutEnd of the deletion it, and backend grouping work packages Begin of the insertionnot taking default value into account for work packagesEnd of the insertion without Begin of the deletion custom fieldEnd of the deletion value Begin of the insertionset.End of the insertion Begin of the deletion as having nil value.End of the deletion

### Screenshots and other files

<img class="op-uc-image op-uc-image_inline" src="/api/v3/attachments/237132/content">

### Environment information

Begin of the deletion _Please check and fill out the following details to help us identify in what versions and distributions of OpenProject the error occurs_

End of the deletion **OpenProject Begin of the deletion installation type**

* Hosted cloud edition

* Packaged installation

* What distribution?

* Docker All-in-one container

* Docker-compose installation

* Other (please specify)


**OpenProjectEnd of the deletion version**

Begin of the insertion_v14.6.3End of the insertion Begin of the deletion _If you&#39;re not running on the cloud edition, please specify the version of OpenProject you&#39;re running. Example: v12.1.5_

**Browser**

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

**Operating System**

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

**Language**

_Please specify the browser languageEnd of the deletion and Begin of the insertionv15.0.0_End of the insertion Begin of the deletion the language of the OpenProject user for which the bug occurred._End of the deletion