Switching from XY to Grid and back causes problems

[duner]

If you switch back and forth between XYChart and ChartGrid the image exports don't keep up with the changes to the state.

Steps to reproduce:

1. Open Chartbuilder to default XYChart page
2. Download image (it's fine)
3. Switch to ChartGrid
4. Download image (it's fine)
5. Switch back to XYChart
6. Download image (it's still a ChartGrid)