Tick label disappears when there is only one

ScottPlot 4.0.48
When there is only one tick visible on an axis, it disappears.

![recording (3)](https://user-images.githubusercontent.com/75701536/106323484-c9ba6b80-6277-11eb-9654-f39696dbd5f7.gif)

