Repro steps:
1. Open Scene1 from the attached project.
2. Select CurveObject and press Play
3. In play mode, move a key in the curve from the Curve script attached to CurveObject (or add a new key).
4. Press undo.
5. Observe the warning in the console: No script asset for CurveEditorSelection. Check that the definition is in a file of the same name.

Notes:
- Not a regression, happens in 2017.1
- Warning does not reproduce if the curve is changed using one of the curve presets
- Warning does not reproduce in edit mode.