Load to Usage rules should show proper validation message - If InstanceId value is not mapped

When we create Load to Usage rules, action page alerts users if they did not map Date, Usage Data Aggregation Level Name. It will be good if we show similar error message, if users did not map InstanceId, InstanceName values.
Right now if we create rule without mapping InstanceId, InstanceNames rule will fail with "Instance info is null or missing" error message