fix(struct): handle undefined fields (#14)

Author: callmehiphop

index.ts

@@ -175,7 +175,7 @@ export const struct = {
    * @param {Struct} struct the protobuf struct.
    * @returns {Object.<string, *>}
    */
-  decode({fields}: Struct): JsonObject {
+  decode({fields = {}}: Struct): JsonObject {
     const json = {};
     Object.keys(fields).forEach(key => {
       json[key] = value.decode(fields[key]);

test.ts

@@ -214,3 +214,8 @@ test('struct.decode', t => {
   const actual = struct.decode(structValue);
   t.deepEqual(actual, obj);
 });
+
+test('struct.decode - undefined fields', t => {
+  const actual = struct.decode({});
+  t.deepEqual(actual, {});
+});