Views warnings when the worth field is aggregated for SUM by an attached taxonomy term

Views warning and notice are produced when the worth field is aggregated for SUM() by an attached taxonomy term as following:
- When the "decimal to 2 places" is selected form the formatter option, the following warning is produced:
Warning: Illegal string offset '#access' in views_handler_field_field->set_items() (line 865 of views/modules/field/views_handler_field_field.inc).
- When the "by currency" is selected form the formatter option, the following warning is produced:
Notice: Undefined index: currcode in mcapi_field_formatter_view() (line 1274 of mutual_credit/mcapi.module).

The warning and notice is visible after the view is saved and its page is visited.