kb fetcher.webOperations('GET', ...) returns falsly response.responseText undefined

[bourgeoa]

from SolidOS/source-pane#17

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.

[timbl]

Interesting ... here is a debugger dump of the response object when this problem arises:

[timbl]

It is strange that the obejct does not have a response.body() getter which https://developer.mozilla.org/en-US/docs/Web/API/Response says it should, as the Response also mixes in:

[bourgeoa]

This is not only a chrome bug only I got it also on firefox.