fix: controller panics due to missing defaults

[dejanzele]

Pull Request Template

Description

Please include a summary of the changes and the related issue (if any). Describe your changes in detail to help reviewers understand your contribution.

• What is the purpose of this PR?
  Scheduler Controller erroring due to missing defaults for Pruner
• What was changed?
  Added better checks and safe guards
• Why was it changed?
  Panics prevent Operator from working and reconciling as expected
• Does this address any existing issues or enhancement requests?

Fixes # (issue)

Type of change

Please select the type of change your PR introduces:

• Bugfix
• Feature
• Code Style Update (formatting, renaming)
• Refactor (code changes that do not fix a bug or add a feature)
• Documentation Update
• Other (please describe):

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions to reproduce these tests. List any relevant details for your test configuration.

• Test Configuration:

  • Kubernetes Version:
  • Helm Version:
  • OS:

• Test Steps:

  1. Step 1
  2. Step 2
  3. ...

Checklist:

• My code follows the style guidelines of this project.
• I have performed a self-review of my code.
• I have commented on my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• 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.
• Any dependent changes have been merged and published in downstream modules.