convert JsonNull to null

src/main/java/com/github/nkzawa/socketio/client/Socket.java

@@ -352,7 +352,7 @@ public class Socket extends Emitter {
     private static List<Object> fromJsonArray(JsonArray array) {
         List<Object> data = new ArrayList<Object>();
         for (JsonElement v : array) {
-            data.add(v.isJsonPrimitive() ? gson.fromJson(v, Object.class) : v);
+            data.add(v.isJsonPrimitive() || v.isJsonNull() ? gson.fromJson(v, Object.class) : v);
         }
         return data;
     }

src/test/java/com/github/nkzawa/socketio/client/ServerConnectionTest.java

@@ -157,18 +157,18 @@ public class ServerConnectionTest {
             @Override
             public void call(Object... objects) {
                 System.out.println("connect:");
-                socket.emit("echo", jsonData, "bar");
+                socket.emit("echo", jsonData, null, "bar");
             }
         }).on("echoBack", new Emitter.Listener() {
             @Override
             public void call(Object... objects) {
-                System.out.println(String.format("echoBack: %s, %s", objects));
+                System.out.println(String.format("echoBack: %s, %s, %s", objects));
                 events.offer(objects);
             }
         });
         socket.connect();
 
-        assertThat(events.take(), is(new Object[] {jsonData, "bar"}));
+        assertThat(events.take(), is(new Object[] {jsonData, null, "bar"}));
         socket.disconnect();
     }