sometimes source-pane display undefined for an existing body

[bourgeoa]

Sometimes source-pane display text undefined for an existing body. (see example below)
When editing original body is lost.
This is reproduceable (do in the same order) and does not appear only for text/plain file, but also text/html file
If you reload the page everything is ok again.
Displaying the sharing-pane seems to be the origin of the problem.

Only seen when a file acl is set.

• text.txt.acl
  
• human readable pane
  
• source-pane
  
• editing the pane edit the word undefined and not the real body and you lose previous content
  

[bourgeoa]

rdflib.js in kb.fetcher.webOperations() is responsible of the problem.
response.responseText on some situation returns undefined.
Replacing by await response.text() returns correctly the body.