According to Crashlytics, this issue only on iOS 12, I can't to reproduce that. There is an assumption that this is due to the toolbar for the keyboard, but what exactly the problem is is not clear.
Attempting to attach a window (<UITextEffectsWindow: 0x1380bfa00; frame = (0 0; 320 480); hidden = YES; layer = <UIWindowLayer: 0x2830cc5e0>>) to a screen with a nil FBSDisplayIdentity