fix inner contour not being generated on all sides
fix inner contour not being generated on all sides

Sometimes the inner contour is very close to the middle.
If only one side of the contour gets generated then a hollow cylinder might get filled,
because the inner contour of only one side of the circle is generated.

With this commit the inner contours always overlap with the walls by 5 micron,
which should be negligible.

Ultimaker/CuraEngine,Ultimaker/CuraEngine