fix: improve curl options in custom_version_command

- Add --fail, --silent, --show-error, --location flags to curl command
- Add // empty fallback to prevent null values when JSON doesn't have version

This improves error handling when fetching the latest Lidarr version.
No changes to auto-generated files (Jenkinsfile, README.md).

Author: ford22

jenkins-vars.yml

@@ -2,7 +2,7 @@
 # jenkins variables
 project_name: docker-lidarr
 external_type: na
-custom_version_command: curl -sL "https://lidarr.servarr.com/v1/update/master/changes?runtime=netcore%26os=linuxmusl" | jq -r '.[0].version'
+custom_version_command: curl --fail --silent --show-error --location "https://lidarr.servarr.com/v1/update/master/changes?runtime=netcore%26os=linuxmusl" | jq -r '.[0].version // empty'
 release_type: stable
 release_tag: latest
 ls_branch: master