When generating the transformation for rest procedure, in the invokeHTTP procedure, use named procedures. aka like

invokeHTTP (action=>'GET', endpoint=>qp, stream=>'true')

this way one can avoid putting the null parametes, as well as if there are additional parameters added to invokeHTTP as did in TEIID-3016 the generated procedure will be error free for next versions. I did see one error here with Teiid 8.9 Alpha, which is logged as TEIID-3107