How to reproduce:
1. Open the “spline_bug“ project
2. Open the “SampleScene“
3. Select the “Spline“ GameObject
4. In the Inspector window, remove the “Spline 0“ from the list in the Spline Container component
5. Add a Spline to the list
5. Observe the Console

Expected result: No exceptions are thrown
Actual result: ArgumentOutOfRangeException is thrown

Reproducible with: 2.5.1 (2021.3.32f1, 2022.3.12f1, 2023.1.19f1, 2023.2.0b16, 2023.3.0a12)

Reproducible on: Windows 10
Not reproducible on: No other environment tested

Error: ArgumentOutOfRangeException: Specified argument was out of the range of valid values.
Parameter name: index