Fix out of bed items after arrange.

Disabled outline decimation for arrange and added very small (EPSILON) safety offset to bed detection boundaries.

src/slic3r/GUI/3DScene.hpp

@@ -611,6 +611,8 @@ struct _3DScene
     static void point3_to_verts(const Vec3crd& point, double width, double height, GLVolume& volume);
 };
 
+static constexpr float BedEpsilon = EPSILON;
+
 }
 
 #endif