We are not failing when http body is empty. Tests imported/w3c/webdriver/tests/set_window_rect/set.py::test_null_parameter_value and imported/w3c/webdriver/tests/set_timeouts/set.py::test_null_parameter_value are failing because of this.
Created attachment 360339 [details] Patch
Committed r240648: <https://trac.webkit.org/changeset/240648>
<rdar://problem/47627816>