Allow for text nodes with no text or tail nodes (such as footnote elements with no whitespace befor the next footnote element)
Allow for text nodes with no text or tail nodes (such as footnote
elements with no whitespace befor the next footnote element)

This change is required for EdgarRenderer of inline footnotes
and for OIM database loading of footnotes when the footnote
element has no trailing whitespace.

sternshus/Arelle,sternshus/Arelle,sternshus/Arelle,sternshus/Arelle,sternshus/Arelle