Negative radius check implemented

Comparison/src/main/java/cz/fidentis/analyst/visitors/mesh/PrioritySphere.java

@@ -41,13 +41,16 @@ public class PrioritySphere extends MeshVisitor  {
      * 
      * @param sphereCenterPosition Position of the center of the sphere in which
      *                             the priorities will be calculated
-     * @param sphereRadius Radius of the sphere
+     * @param sphereRadius Radius of the sphere (must be greater than or equal to 0)
      */
     public PrioritySphere(Point3d sphereCenterPosition, double sphereRadius) {
         if (sphereCenterPosition == null) {
             throw new IllegalArgumentException("sphereCenterPosition");
         }
         this.sphereCenterPosition = sphereCenterPosition;
+        if (sphereRadius < 0) {
+            throw new IllegalArgumentException("sphereRadius");
+        }
         this.sphereRadius = sphereRadius;
     }