Missing config schema error when using delimited text

Problem/Motivation

When a scheduled task is set, there are config errors:

task_settings.exporter_settings.delimiter		;	missing schema	
task_settings.exporter_settings.excel		true	missing schema

Steps to reproduce

* Add scheduled task "export and email results" to a webform
* choose delimited text
* delimiter semicolon
* enable excel compatible file

check config status with config inspector module.

Note:
when using XLSX as exporter, this problem is solved, but for delimited text it should be fixed.