[3.13] pythongh-131339: test PyBytes_Size for a zero-size bytes object (pythonGH-131340) (python#131343)

pythongh-131339: test PyBytes_Size for a zero-size bytes object (pythonGH-131340)
(cherry picked from commit 3ae67ba)

Co-authored-by: Nybblista <170842536+nybblista@users.noreply.github.com>

Author: miss-islington

Lib/test/test_capi/test_bytes.py

@@ -93,6 +93,7 @@ def test_size(self):
         # Test PyBytes_Size()
         size = _testlimitedcapi.bytes_size
 
+        self.assertEqual(size(b''), 0)
         self.assertEqual(size(b'abc'), 3)
         self.assertEqual(size(BytesSubclass(b'abc')), 3)
         self.assertRaises(TypeError, size, bytearray(b'abc'))