Handle nil terminals in Clusters::Platforms::Kubernetes

What does this MR do?

Handle nil terminals in Clusters::Platforms::Kubernetes. I'm not very familiar with this class/logic but the fix seems straightforward.

What are the relevant issue numbers?

Closes #55551 (closed).

Does this MR meet the acceptance criteria?

• [-] Changelog entry added, if necessary
• [-] Documentation created/updated
• Tests added for this feature/bug
• Tested in all supported browsers
• [-] Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• [-] Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer