fix legacy slice/top conversion

src/add/array.js

@@ -91,11 +91,7 @@ AP.addOnce = function(val) {
  * shallow cloning with clone(arg) call on each new element
  */
 AP.clone = function() {
-    let na = this.slice(),
-        ln = na.length,
-        i = 0;
-    while (i < ln) na[i] = na[i++].clone(...arguments);
-    return na;
+    return this.map(v => v.clone(...arguments));
 };
 
 AP.xray = function(arg) {

src/kiri/slice.js

@@ -147,7 +147,7 @@ class Slice {
         if (data.length) {
             // standard legacy polygon
             let top = new Top(data);
-            this.tops.push(data);
+            this.tops.push(top);
             top.simple = data;
             return top;
         } else {