blank log path should not log to file

[aphralG]

Proposed changes

If log path in nginx-agent.conf is left blank no log file is used and logs only go to stdout/stderr

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING document
• I have run make install-tools and have attached any dependency changes to this pull request
• If applicable, I have added tests that prove my fix is effective or that my feature works
• If applicable, I have checked that any relevant tests pass after adding my changes
• If applicable, I have updated any relevant documentation (README.md)
• If applicable, I have tested my cross-platform changes on Ubuntu 22, Redhat 8, SUSE 15 and FreeBSD 13

[netlify]

✅ Deploy Preview for agent-public-docs ready!

Name	Link
🔨 Latest commit	a23445c
🔍 Latest deploy log	https://app.netlify.com/sites/agent-public-docs/deploys/64d38d7c87f84b0008cfcca4
😎 Deploy Preview	https://deploy-preview-427--agent-public-docs.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[codecov-commenter]

Codecov Report

Patch coverage has no change and project coverage change: +0.16% 🎉

Comparison is base (3d9d248) 67.43% compared to head (106199f) 67.59%.
Report is 3 commits behind head on main.

❗ Your organization is not using the GitHub App Integration. As a result you may experience degraded service beginning May 15th. Please install the Github App Integration for your organization. Read more.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #427      +/-   ##
==========================================
+ Coverage   67.43%   67.59%   +0.16%     
==========================================
  Files         113      113              
  Lines       12764    12764              
==========================================
+ Hits         8607     8628      +21     
+ Misses       3588     3567      -21     
  Partials      569      569              

Files Changed	Coverage Δ
src/core/config/defaults.go	0.00% <ø> (ø)

... and 1 file with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.