Error when Multi-Select Dropdown Control as Filter with Multiple Values Selected

[Mark Dewes]

I have a multi-select dropdown control 'Assignee' from the `Issue`.`Assignee Account ID` field used to filter my charts by adding this formula column to the Chart:  

CASE WHEN {ASSIGNEE.IN('"Assignee"')} THEN 1 WHEN {ASSIGNEE} = "Unassigned" AND "Assignee account ID" is NULL then 1 ELSE 0 END

When a single value is selected in the control or the control is blank, the chart works as expected. But when the user selects multiple values in the control, the chart errors. Since I don't have a comma in my Custom Formula syntax, I'm assuming it is when the "ASSIGNEE.IN()" parsing multiple values. Help?

Warning

[SQLITE_ERROR] SQL error or missing database (near ",": syntax error)