Summary:
Editing data selection would sometimes cause columns to be hidden in the updated view. A
missing conditional was the culprit: generally, field visibility shouldn't be modified after the view is
updated, but we make an exception for charts to keep certain fields visible or hidden between
updates, so that chart configuration doesn't change too significantly and cause unexpected
data to be displayed. This special behavior for charts was erroneously being applied to non-charts
as well.
Also, when no columns were visible in a view, opening the row menu would cause an error to be
thrown. A loop was inadvertently using null control variables - an explicit check for non-null loop
variables was added, which skips the loop when no columns are visible.
Test Plan: Browser tests.
Reviewers: jarek
Reviewed By: jarek
Subscribers: jarek
Differential Revision: https://phab.getgrist.com/D3650
