ID 217359 - Adding points after cusping a B-Spline puts the point in the wrong place

Problem summary
When adding points to a cusped B-Spline, then the new point is created in the wrong place.

Steps to reproduce

 

To reproduce:

- Draw (a closed) spline with the B-Spline tool
- Add a new point somewhere by holding down Ctrl+Alt

Works as expected.
- Select all points and cusp them (Shift+Z).
- Add a new point somewhere

The point is not added correctly:

 

Regression testing back to 6.0v1 shows that this never worked.