Error "Cannot read properties of null (reading 'project')" is shown when installing GitLab Agent from the Agent tab
### Summary
Error `Cannot read properties of null (reading 'project')` is shown when installing Agent from the Agent tab.
### Steps to reproduce
- create an empty test project
- in this project, create an empty file `.gitlab/agents/agent001/config.yaml`
- go to **Infrastructure > Kubernetes clusters**, switch to `Agent` tab and click `Connect with the GitLab Agent`, select `agent001` in the list and click `Register`
### Example Project
https://gitlab.com/gitlab-gold/atanayno-kas-test
### What is the current *bug* behavior?
The following error is shown when doing it in Chrome:
```text
Failed to register an agent
Cannot read properties of null (reading 'project')
```
In Firefox it is a bit different:
```text
Failed to register an agent
t is null
```
### What is the expected *correct* behavior?
You should be able to reach the next step, obtain the registration token, and the command to install the Agent.
### Relevant logs and/or screenshots

No errors are shown in the browser's dev console.
### Output of checks
This bug happens on GitLab.com. I was not able to reproduce this issue with a self-managed instance of GitLab 14.7.3
### Workaround
It works fine if you create an Agent from the tab `All`
issue