Check if cartographic is defined in clipping plane setup

[lilleyse]

Follow up to #7182. A tileset with a bounding sphere center exactly at (0, 0, 0) would cause a crash in the clipping planes setup.

Anyone could review this, but maybe @hpinkos?

[cesium-concierge]

Thanks for the pull request @lilleyse!

• ✔️ Signed CLA found.
• ❔ CHANGES.md was not updated.
  • If this change updates the public API in any way, please add a bullet point to CHANGES.md.

Reviewers, don't forget to make sure that:

• Cesium Viewer works.
• Works in 2D/CV.
• Works (or fails gracefully) in IE11.

---

I am a bot who helps you make Cesium awesome! Contributions to my configuration are welcome.

🌍 🌎 🌏

[hpinkos]

Looks good, thanks @lilleyse