Unidentified circle object

Inside my Revit file consist of a piece of square slab and a model line, (both created by me)
After running my dynamo script. I will find a 99.5m blue circle appears in my Revit model.

My script will get all line in the model and if line intersects with slab. divide the slab using the line
The weird thing about this circle is it will cuts my slab. and if my slab is outside of this circle. my script won’t work.

Please tell me where did that circle come from. and how to solve it.

Thanks

SLAB_BREAK_FINAL - TEST VER 1.dyn (20.6 KB)

slab.rvt (1.7 MB)