avoid infinite recursion

lib/index.js

@@ -137,8 +137,12 @@ Cow.prototype.finish = function Cow_finish() {
 	 * replace those references with an extra pass
 	 */
 	function replaceProxies(obj) {
-		if (typeof obj !== 'object')
+		if (!obj || typeof obj !== 'object')
 			return obj;
+		// avoid cycles
+		if (seen.has(obj))
+			return;
+		seen.add(obj);
 		var copied = proxyCopies.get(obj);
 		if (copied)
 			return copied;

package.json

@@ -3,7 +3,7 @@
   "description": "copy on write deep, cyclic js objects",
   "keywords": ["cow", "copy on write", "copy-on-write", "copy"],
   "main": "./index",
-  "version": "0.2.0",
+  "version": "0.2.1",
   "maintainers": [
     "Arpad Borsos <arpad.borsos@googlemail.com> (http://swatinem.de)"
   ],

test/cow.js

@@ -131,6 +131,7 @@ describe('Cow', function () {
 		var p = c.proxy;
 		p.child.new = p.child;
 		p.child.new2 = {child: p.child, child2: {}};
+		p.child.new2.child2.child2 = p.child.new2.child2;
 		var f = c.finish();
 		f.child.should.not.equal(o.child);
 		f.child.new.should.equal(f.child);