I had the exact same thing happen to me with the exact same style of door (I am assuming a glass curved sliding half door.). Something about them being jammed and when you lift it releases all the pressure and the whole thing shattered.

Always hated those doors, they always come of their railings and are annoying to clean.

Anyway, thankfully mum was just like "well now I have an excuse to replace the shower" so it was all good.