Quick launch camera function doesn't work

Hi,

When I try to use the quick launch camera (when iphone is still locked) on my iphone my screen turns black, and I can't make any pictures. When I slide up slowly it shows the camera view, but when it is completely slided up the screen turns black and I can't make any pictures.

The normal camera function (using when phone is unlocked) works fine.

I've got an iPhone 6 version 8.1 (which i don't want to upgrade)

Thanks