Fix #7445: a return annotation `None` is not converted to a hyperlink

tests/test_domain_py.py

@@ -239,6 +239,7 @@ def test_get_full_qualified_name():
 def test_parse_annotation():
     doctree = _parse_annotation("int")
     assert_node(doctree, ([pending_xref, "int"],))
+    assert_node(doctree[0], pending_xref, refdomain="py", reftype="class", reftarget="int")
 
     doctree = _parse_annotation("List[int]")
     assert_node(doctree, ([pending_xref, "List"],
@@ -266,6 +267,12 @@ def test_parse_annotation():
                           [pending_xref, "int"],
                           [desc_sig_punctuation, "]"]))
 
+    # None type makes an object-reference (not a class reference)
+    doctree = _parse_annotation("None")
+    assert_node(doctree, ([pending_xref, "None"],))
+    assert_node(doctree[0], pending_xref, refdomain="py", reftype="obj", reftarget="None")
+
+
 
 def test_pyfunction_signature(app):
     text = ".. py:function:: hello(name: str) -> str"