Sleep screen cover in crop mode is not vertically centered

### Affected Version

0.14.0-dev

### Describe the Bug

Sleep screen cover in crop mode is not vertically centered

### Steps to Reproduce

1. Set sleep screen to cover, cover mode to crop
2. Open a book with a cover that's taller than the X4 screen
3. Go to sleep

### Expected Behavior

Cover should be vertically centered.

### Relevant Log Output/Screenshots

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