Ignore updates to fields that weren't defined by this class.

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@6329 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/main/resources/com/threerings/presents/tools/streamable_as.tmpl

@@ -92,6 +92,8 @@ class Signaller
                 signal = _obj.{{name}}Changed;
                 break;
 {{/fields}}
+            default:
+                return;
         }
         signal.dispatch(event.getValue(), event.getOldValue());
     }