[jvm] fix anonymous object printing

std/jvm/DynamicObject.hx

@@ -27,13 +27,11 @@ class DynamicObject implements java.lang.Cloneable extends Object {
 		var first = true;
 		try {
 			for (key in _hx_fields.keys()) {
+				if (first) first = false
+				else buf.add(", ");
 				buf.add(key);
 				buf.add(": ");
 				buf.add(_hx_fields.get(key));
-				if (first) {
-					first = false;
-					buf.add(", ");
-				}
 			}
 		} catch(e:Dynamic) {
 			--__hx_toString_depth;