Bug: Error when creating the default pull secret

Description

Creating a default pull secret from a newly created Namespace fails.

The UI sends an invalid request while trying to add a value to the imagePullSecrets array. In this case, the target array does not exist yet, but the request attempts to add an item to it. As a result, the API rejects the request and the default pull secret is not created.

Steps to reproduce

1. Open the console connected to a clean Kubernetes cluster.
2. Go to Namespaces.
3. Create a new Namespace.
4. Open the newly created Namespace details page.
5. Click the action to create a default pull secret.
6. Enter a secret name.
7. Click Save.

Actual result

The operation fails with the following error:

HttpError: the server rejected our request due to an error in our request

Expected result

The default pull secret should be created successfully and displayed on the Namespace page.

Additional details

This was reproduced on the main (49745c2) branch with "pure" k8s cluster.

https://github.com/user-attachments/assets/3a04035a-f6be-4d6e-a3eb-2548cd89bc26

Start at the Namespace details page's action for creating a default pull secret and inspect how the request updates the imagePullSecrets array when the array is absent. Reproduce the steps on a clean Kubernetes cluster, then confirm the request succeeds and the created secret appears on the Namespace page.