Sound is not played in push notifications

I am using iOS 7 and my push notifications do not play sounds.

Strangely, I found there is no setting for sound in the Preference > Notification Center for my app. Following is the screenshots of Notification center for my app:

And following is that for Skype:

You see, there is no 'Sounds' section for my app.

Could anyone help?

Update:

Now I have registered sound in my app. The Notification Center now looks like:

and my notification has sounds. Looks good.

But after I enter the setting of my app, there is initially a 'Sounds' section like Skype, but then the Preference app crashed, and after that, there is no more 'Sounds', just like below:

Might it be a bug of Apple?