Spline points with NaNs cause Unity to crash without reporter

I used Spline::InsertPointAt() to add a spline point and had some bad math that resulted in NaNs. This caused a Unity editor crash that did not get caught by the bug catcher that lets you submit a crash dump.

@adamzl Could you please file a bug report with simple repro case ? We will take a look asap.

https://fogbugz.unity3d.com/default.asp?1108671_mlal0p5hcdnc7jph