Error listing ngwaf customsignal within workspace.

**Version** ```sh Fastly CLI version v13.3.0 (0719b16c) Built with go version go1.24.11 darwin/arm64 (2026-02-02) ``` **What happened** Please describe the command you ran, what you expected to happen, and what happened instead. ```sh fastly ngwaf workspace customsignal list -v --workspace-id=<anything valid> ``` I expected to get a valid listing back as a result... instead I get an error: ```sh Fastly API endpoint: https://api.fastly.com Fastly API token provided via config file (profile: user) ERROR: failed to decode json response: parsing time "" as "2006-01-02T15:04:05Z07:00": cannot parse "" as "2006". ```