logscale with event type has bad y axis limits

[devkev]

Specifically, it goes down to 1e-7. This is a problem when overlaying with (say) a regular scatter plot that you want to show in logscale. Without the event overlay, the y axis correctly starts at 1e0. With the event overlay, you have to zoom in to the full x range, from 10^0 up to the top of the graph.