I made a world to try out the vibrant visuals and the happy ghast. It loaded in fine. Everything was good. Had to turn on the vibrant visuals through the settings. When I closed the settings menu the screen was completely blacked out. Could only see some text at the top, coordinates and the buttons used to move the character. Tried to move and the character moved according tothe coordinates, so I turned it off and the screen went back to the normal look it had when I first loaded it in. But every time I try to turn on the vibrant visuals it blacks the screen out.
This issue is being tracked at MCPE-203972.