map highlight only updates when scrolling upwards on small files

[daviddeutsch]

Both scrolling down in the code view and the minimap - whether by mousewheel or dragging the mouse - leaves the highlight in place if the file is short (less than 100 lines for me). Only moving the text cursor reliably updates the minimap highlight down.

My guess is that this is related to 100 lines not filling an entire second screen. With longer files, I see a similar lag until I scroll beyond the first "page break".