#109 Crash due to NullReferenceExeption in SetRange()

[ingineer]

ZedGraph crashes due to a NullReferenceException in SetRange() called by AxixChange().

In SetRange() on lines 2692 and 2699 (ZedGraph version 5.1.5), pane.YAxis and pane.Y2Axis are referenced without first checking whether they are null.