f:ins not displayed when element content only

[gerritbruening]

Seems as if f:ins is not displayed when it has no text() as descendant.
See
https://github.com/faustedition/faust-xml/blob/264f58b854cc292a56e16d10c52ed9116b95d649/xml/transcript/gsa/391098/0147.xml#L338
and

(http://dev.faustedition.net/document?sigil=2_H&page=139&view=document)