### Steps to reproduce

1. Navigate to a work package
2. Click on "Share" to open the Share modal
3. From the dropdown, select a Locked User
4. Click on "Share"

### What is the buggy behavior?

The modal grows to fullscreen. This is because a non-successful response is returned. The members contract has a validation where a user must not be locked in order to become a member (and this makes sense).

### What is the expected behavior?

Begin of the insertion* Locked users shouldEnd of the insertion Begin of the deletion The locked user isEnd of the deletion not Begin of the deletion a selectable from the dropdown. The locked user must stillEnd of the deletion be Begin of the insertionshownEnd of the insertion Begin of the deletion a disabled optionEnd of the deletion in the Begin of the deletion dropdown.

### Important note

Not returning the locked user in theEnd of the deletion list Begin of the insertion
* IfEnd of the insertion Begin of the deletion of available principals might lead the sharer to believe that the locked user probably doesn't exist and would try inviting him. This would lead toEnd of the deletion a Begin of the insertionusers enters an email which existsEnd of the insertion Begin of the deletion very confusing situationEnd of the deletion for Begin of the insertiona locked user, an error message is shown stating thatEnd of the insertion the Begin of the insertionusers is lockedEnd of the insertion Begin of the deletion sharing user.End of the deletion

### Environment information

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

**OpenProject installation type**

* [ ] Hosted cloud edition
* [ ] Packaged installation
* What distribution?
* [ ] Docker All-in-one container
* [ ] Docker-compose installation
* [ ] Other (please specify)

**OpenProject version**

https://github.com/opf/openproject/commit/472eee17b3353827b3fe30844b28013accf629de

**Browser**

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