Fix crash when reloading displayable text view.
Fix crash when reloading displayable text view.

I forgot that -operationDidReturnWithLyrics: would not always be called
in the main thread. Also rewritten -reloadDisplayableTextView... to be
simpler to read (it's not slow, so why trade performance for
illegibility?), and added safety checks before each objc_msgSend to
prevent crashing.

precocity/FetchMyLyrics