Scrolling does not slow down if the document is too short

[openjck]

Steps to reproduce

1. Create a new file with 30 lines
2. Enter normal mode
3. Type gg
4. Type CTRL-F

Expected result

The scrolling slows as it nears the final line.

Actual result

The scrolling does not slow as it nears the final line.

[openjck]

This might be a duplicate of #28. That issue isn't written very clearly, so I'm not exactly sure what it's supposed to be about, but it sounds similar.