fix: Users without XP don't show in Leaderboard

[cjmellor]

Description

When running the Leaderboard service, it was also showing Users' without XP, which did not make sense.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Related Issues and Pull Requests

• Issue #...
• PR #...

Testing

Please provide a passing test where possible. This package uses PestPHP

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have made corresponding changes to the documentation [OPTIONAL]