fix: bind prototype chain callback of custom element descriptor

Author: btford

Diff for: zone.js

@@ -589,7 +589,7 @@ Zone.patchRegisterElement = function () {
       if (opts.prototype[callback]) {
         var descriptor = Object.getOwnPropertyDescriptor(opts.prototype, callback);
         if (descriptor.value) {
-          descriptor.value = zone.bind(descriptor.value);
+          descriptor.value = zone.bind(descriptor.value || opts.prototype[callback]);
           Zone._redefineProperty(opts.prototype, callback, descriptor);
         }
       }