Summary: Math functions like SUM which call `_chain` were catching `TypeError`s raised by the iterable arguments themselves, e.g. `SUM(r.A / r.B for r in $group)` where `r.A / r.B` raises a `TypeError` would silently return wrong results. This diff narrows the `try/catch` to only check whether the argument is iterable as intended, but not catch errors from the process of iterating.
Test Plan: Added Python unit test.
Reviewers: jarek
Reviewed By: jarek
Differential Revision: https://phab.getgrist.com/D3679
aa88c156e6