resolver: Don't crash on nil objs

[DolceTriade]

If a YAML specifies an empty initContainers:, this will crash this code if we also specify yamls. regardless of how pointless this is, this is, it is valid k8s yaml that applies cleanly.

Related Issue

Fix #141

Motivation and Context

Fixes crash

How Has This Been Tested?

No longer crashes

Types of changes

• [x] 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 change)

Checklist:

• [x] I have signed the Adobe Open Source CLA.
• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.

[michaelschiff]

Thanks for the contribution! Mind adding a test for this case?

[DolceTriade]

Sorry I missed your comment. Added a test case that crashes on main but not on my branch. PTAL, thanks!