[bug] Hide empty usage box when RadiusGroup has no checks #819

[Unnati-Gupta24]

Checklist

• I have read the OpenWISP Contributing Guidelines.
• I have manually tested the changes proposed in this pull request.
• I have written new test cases for new code and/or updated existing tests for changes to existing code.
• I have updated the documentation.

Reference to Existing Issue

Closes #819 .

Description of Changes

Fixed an issue where an empty box was being displayed in the status page when a user's RadiusGroup had no defined checks. For example, when a user belonged to the power-users group which doesn't define any usage checks, an empty box would still appear where usage information should be shown.

Changes

Modified client/components/status/status.js to properly handle cases when the API returns no checks:

• Added check for empty checks array before setting userChecks
• Explicitly set userChecks to null and disable radius usage display when no checks exist
• Only enable radius usage display when there are actual checks to show

Before this change, even with no checks, the UI would still show an empty box. Now, when a user's RadiusGroup has no checks defined, no empty box will be displayed, providing a cleaner user interface.

Screenshot

All tests has been passed after changes

@pandafy kindly review this