VersionAlert for Unity

[SPLB-275] Fixed a bug where the `SplineContainer` component would throw warning when entering playmode.
[SPLB-266] Fixed a bug where instantiating a `SplineExtrude` component at runtime would throw errors.
[SPLB-269] Fixed a bug where instantiating a `SplineAnimate` component at runtime would throw errors.
[SPLB-260] Fixed a bug where playing a `SplineAnimate` from a start method would not work.
[SPLB-267] Fixed a bug where undoing a spline insertion in a container would throw errors from the `SplineInstantiate` component.
[SPLB-261] Fixed a bug where the knot placement tool would not work when multiple scene views were opened.
[SPLB-253] Fixed a bug where using the knot placement tool in 2D mode would not work if the grids are turned off.
[SPLB-258] Fixed a bug where destroying a component would throw errors in the console.

com.unity.splines 2.6.1