[dashboard] fix: showing secrets with empty values (#1480)

Signed-off-by: Andrei Kvapil <kvapss@gmail.com>

<!-- Thank you for making a contribution! Here are some tips for you:
- Start the PR title with the [label] of Cozystack component:
- For system components: [platform], [system], [linstor], [cilium],
[kube-ovn], [dashboard], [cluster-api], etc.
- For managed apps: [apps], [tenant], [kubernetes], [postgres],
[virtual-machine] etc.
- For development and maintenance: [tests], [ci], [docs], [maintenance].
- If it's a work in progress, consider creating this PR as a draft.
- Don't hesistate to ask for opinion and review in the community chats,
even if it's still a draft.
- Add the label `backport` if it's a bugfix that needs to be backported
to a previous version.
-->

## What this PR does


### Release note

<!--  Write a release note:
- Explain what has changed internally and for users.
- Start with the same [label] as in the PR title
- Follow the guidelines at
https://github.com/kubernetes/community/blob/master/contributors/guide/release-notes.md.
-->

```release-note
[dashboard] fix: showing secrets with empty values
```

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Bug Fixes**
* Fixed base64 extraction for secret data in the dashboard so secret
values are parsed and shown correctly.
* Addresses cases where secret fields could appear blank or incorrect
due to parsing issues.
* Improves consistency and reliability of secret-related columns across
dashboard views, reducing confusion and manual checks.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

internal/controller/dashboard/static_helpers.go

@@ -972,7 +972,7 @@ func createSecretBase64Column(name, jsonPath string) map[string]any {
 					"data": map[string]any{
 						"id":             "example-secretbase64",
 						"plainTextValue": "hello",
-						"base64Value":    "{reqsJsonPath[0]['" + jsonPath + "']['-']}",
+						"base64Value":    "{reqsJsonPath[0]['" + jsonPath + "']['']}",
 					},
 				},
 			},