No validation error from Arelle

[SK]

Dear all,

An empty string as a tagged fact  (in an iXBRl instance) does not seem to trigger an error by Arelle. 

E.g.

<ix:nonFraction name="ifrs-full:DividendsPaid" format="ixt:fixed-zero" decimals="-5" scale="6" unitRef="EUR" contextRef="D2020-01-01-2020-12-31-OtherReservesMember"></ix:nonFraction>

However, as I understand the specifications, it should not pass without an error:

https://www.xbrl.org/specification/inlinexbrl-part1/rec-2013-11-18/inlinexbrl-part1-rec-2013-11-18.html#d1e5220

10.1.1 Constraints on ix:nonFraction": 

- The ix:nonFraction element MUST have exactly one child which SHALL be either an ix:nonFraction element or a text node, unless it has an xsi:nil attribute with the value true.

... furter:

- The text node child, if present, MUST be a non-empty string.

Thanks for any help with this and kind regards