Trying to define a condition for the delete behavior in the processing tab for a Sync Editor workflow step. We want to only delete accounts that are not of a certain type which is defined in a custom string column. Now this works for accounts that have this custom column populated, however, if the column is null, then those accounts are not recognized and therefore, not deleted. So to fix this we tried including a "<custom column> is null" expression in the condition, however, we are not allowed to use the "IS" operator. How can we account for null columns in the condition?