Datagrid open/close row group indicator does not work on the TOTAL row when a split_by is present

[texodus]

Steps to Reproduce:

1. Create a datagrid view with at least one group_by and split_by
2. Click the open/close indicator next to the first row, TOTAL.

Expected Result:

The TOTAL row to close, leaving just this row present in the datagrid

Actual Result:

Nothing

Additional Context:

Shift+Click on a row group in the datagrid will expand/collapse all groups to that group's level. Collapsing, then expanding, a parent row in order to force all child groups to collapse seems to have evolved as a common usage pattern for Perspective, though this was never the intended workflow to accomplish this, and in fact it may make sense in the course of resolution of this issue to remove expand/collapse on a Datagrid's TOTAL row entirely.

In the video below, various row group levels are clicked with the Shift key held:

shift+click.mov