Bug with fillet causing solid to disappear

The following code causes the solid body to disappear and it leaves some surfaces only:
```python
import cadquery as cq

result = (
cq.Workplane('YZ')
.cylinder(75, 40)
.faces('>X')
.workplane()
.transformed(rotate=(-45,0,0))
.split(keepBottom=True)
)

result = result.edges('|Y').fillet(4)
```

Note that **increasing** the fillet value to 5 seems to work OK: