[Bug] SIGHUP complains about ACL errors when no ACL is configured

[nblock]

Is this a support request?

• This is not a support request

Is there an existing issue for this?

• I have searched the existing issues

Current Behavior

When no ACL is configured and headscale receives a SIGHUP it prints the following error message:

2024-12-14T19:42:19+01:00 INF Received SIGHUP, reloading ACL and Config signal=hangup
2024-12-14T19:42:19+01:00 ERR failed to set new policy error="parsing policy: parsing hujson, err: hujson: line 1, column 1: parsing value: unexpected EOF"

Expected Behavior

Only process and print policy related errors on SIGHUP when a policy is configured.

Steps To Reproduce

1. Use the following configuration (default):

policy:
  # The mode can be "file" or "database" that defines
  # where the ACL policies are stored and read from.
  mode: file
  # If the mode is set to "file", the path to a
  # HuJSON file containing ACL policies.
  path: ""

2. Send SIGHUP: kill -HUP $(pidof headscale_0.24.0-beta.1_linux_amd64)
3. Headscale logs:

024-12-14T19:45:24+01:00 INF Received SIGHUP, reloading ACL and Config signal=hangup
2024-12-14T19:45:24+01:00 ERR failed to set new policy error="parsing policy: parsing hujson, err: hujson: line 1, column 1: parsing value: unexpected EOF"

---

This works fine on Headscale 0.23.0: kill -HUP $(pidof headscale_0.23.0_linux_amd64):

2024-12-14T19:46:35+01:00 INF Received SIGHUP, reloading ACL and Config signal=hangup

Environment

- OS: Arch
- Headscale version: 0.24.0-beta.1
- Tailscale version: -

Runtime environment

• Headscale is behind a (reverse) proxy
• Headscale runs in a container

Anything else?

No response