"open in" menu button from item preview page does nothing when no apps can open the file

I did a preview of an mp3, and the preview showed and worked fine after downloading, but the left-hand 'open in' button does nothing. It is enabled but shows no menu when clicked. Looking at the code, it appears that the presentOpenInMenuFromBarButtonItem function just does nothing and returns NO, which our code ignores, in the case where no apps can open the file.

Since it doesn't look like there's a clean way to check if there are apps that can open it, and then disable the button, I think the best we can do is display an explanation when the function returns NO.