Fix CoordinateList.clone() to copy correctly (#1168)

Author: dr-jts

modules/core/src/main/java/org/locationtech/jts/geom/CoordinateList.java

@@ -242,7 +242,7 @@ public Coordinate[] toCoordinateArray(boolean isForward)
   public Object clone() {
       CoordinateList clone = (CoordinateList) super.clone();
       for (int i = 0; i < this.size(); i++) {	  
-          clone.add(i, (Coordinate) this.get(i).clone());
+          clone.set(i, (Coordinate) this.get(i).clone());
       }
       return clone;
   }

modules/core/src/test/java/org/locationtech/jts/geom/CoordinateListTest.java

@@ -24,9 +24,16 @@ public void testReverseEmpty() {
     checkValue(coordList().toCoordinateArray(false) );
   }
 
+  public void testClone() {
+    CoordinateList clone = (CoordinateList) coordList(0,0,1,1,2,2).clone();
+    checkValue(clone.toCoordinateArray(true), 0,0,1,1,2,2);    
+  }
+  
+  //======================================
+  
   private void checkValue(Coordinate[] coordArray, double ... ords) {
 
-    assertEquals( coordArray.length * 2, ords.length);
+    assertEquals( "list has wrong length", coordArray.length, ords.length / 2);
 
     for (int i = 0 ; i < coordArray.length; i += 2) {
       Coordinate pt = coordArray[i];