Miche tree GUI connecting lines stop rendering while they are still visible (culling)

[hhyyrylainen]

The culling near the edges with the margins doesn't work fully correctly, here's a line that stopped rendering too early:

Dragging the view a bit to the left makes it draw again:

The line culling algorithm should be changed a bit to fix that. I think that maybe the somewhat recent evolutionary tree margin changes fixed a similar issue there.