Bug: Line Chart Export/Cart Don't Match

[danglorioso]

Describe the bug

Exported line charts and cart previews with Group By applied so not match the chart displayed on the charts page. For example, with group by division, the legend shows 6 categories while the charts page shows 4 categories. Some of the group by show the wrong group by in the exported figure.

Where Is Bug/How to Recreate

Steps to reproduce the behavior:

1. Go to line chart
2. Add a chart with a "Group By" to cart
3. Both cart preview and export is wrong chart

Expected behavior

Suggested fix(es):

Screenshots

Other comments

[tika]

This will be fixed by same pr for #185