Describe the feature or problem you’d like to solve

When using gh cache list --json <fields> in a repository without workflow caches, the command outputs a error message instead of JSON.

$ gh cache list --json id
No caches found in <repository name>

This behavior breaks JSON parsing in automated scripts since they expect valid JSON output and they need extra error handling.
For consistent JSON output format, the output should be [].

Proposed solution

When the --json option is used, gh cache list should retuan an empty JSON array ([]) to indicate no caches exist.

$ gh cache list --json id
[]

The text message should still be shown when running without the --json flag.

Additional context

• gh version: gh version 2.60.1 (2024-10-25)