When the user switched the vertical axis from left to right (or right to left)...

When the user switched the vertical axis from left to right (or right to left) the vertical axis was missing briefly and has been fixed.  In Toolbar -> Chart Axis, when updating and the selected axis is not valid, set the axis to the opposite of the last valid index (i.e.: If the last selection was Left and Left is no longer valid, default to the Right axis).