[BUG]: Incorrect interval constraint normalization for contours.value in contour traces #8124

Description

For interval constraints, contours.value is expected to contain two values.

Currently, invalid-length arrays are normalized incorrectly.

CodePen: https://codepen.io/Lexachoc/pen/EaWEpLx

Note

This also affects contourcarpet, which reuses the same constraint defaults.