Cursor moves to thought hidden by autofocus

## Steps to Reproduce

```
- a
  - b
    - c
- d
``` 

1. Set the cursor on `c` so `d` disappears
2. Tap 1 line height below `c`, to the right of where `d` would be. 

## Current Behavior

Cursor moves to `d`. 

## Expected Behavior

Cursor should move to `b`. 

Tapping on empty space with no visible thoughts to the left or right should always activate `cursorUp`. 