No def not, it's definitely a bug :/
The game lag for a bit then it's a infinite blackscreen. The music continue to play and if I touch my screen it makes sounds (like I would actually click on a button in the game) but I can't see anything
Don't worry, your currency go down, but when you will get to 0 you will still be able to buy things :) (Except for the hogwart match, which you actually need the amount and can't be to 0)