# Possible bug : curve undefined

In order to create the following animated GIF:

I uses the following GGB:

When you open the GGB, and enable animation for slider f, you will find both curves h and i become "undefined".

By copying

First, when I initially created the curve via

- Curve[r cos(v) - r + 2 + cos(v) (1 + sin(5r (π / r + v))), r sin(v) + sin(v) (1 + sin(5r (π / r + v))), v, -2π / r, 2π / r]

without closing and re-openning the GGB, then it worked successfully in obtaining the GIF;

So there should be no problem in either the slider or the algorithm;

second, I tried to edit the objective properties of the curve, by adding "f>=0" to "condition to show object" in Advanced tab, it seems the problem disappears: even I close and reopen the GGB, there is no "curve undefined" problem any more. Or the "condition to show object" in Advanced tab would disappear when curve becomes undefined!

So still I think this might be a bug.