Fix vector polyline clamping

[ggetz]

This fixes a regression from 6e5e7a0#diff-9c322fcbd2bf3549f60528f6659332e11465537ef57caefcc5bae56e7af3a356 which occurs when clamping a vector tileset.

We plan on releasing this as a patch release, so this is targeted for a 1.94.3-release branch. After this is merged and release, we will also merge it into main.

[cesium-concierge]

Thanks for the pull request @ggetz!

• ✔️ Signed CLA found.
• ❔ Unit tests were not updated.
  • Make sure you've updated tests to reflect your changes, added tests for any new code, and ran the code coverage tool.

Reviewers, don't forget to make sure that:

• Cesium Viewer works.
• Works in 2D/CV.

[ggetz]

Thanks @ephjos for verifying this fix!