Fix bug where distance would be too close to 0 to register

the furthest_distance now starts at -1 instead of 0 - if there's a point with a distance of 0, that's fine.

This caused issues in the circle previously.

Quickhull.h

@@ -63,7 +63,7 @@ private:
 
         // Find the point which is furthest away from the line, add it to the output
         Point furthest_point;
-        float furthest_distance = 0.0;
+        float furthest_distance = -1.0;
 
         for (const Point &point : input)
         {