Fix reference leak in ctypes _build_result()

In _ctypes._build_result(), a result tuple is allocated when numretvals > 1.
If v becomes NULL during result construction, the function returns early
without DECREF'ing the tuple, leaking a reference.
Add Py_XDECREF(tup) before returning when numretvals > 1 and v == NULL.

Signed-off-by: Yongtao Huang <yongtaoh2022@gmail.com>

Author: hyongtao-code

Modules/_ctypes/_ctypes.c

@@ -4557,6 +4557,7 @@ _build_result(PyObject *result, PyObject *callargs,
             v = PyTuple_GET_ITEM(callargs, i);
             v = PyObject_CallMethodNoArgs(v, &_Py_ID(__ctypes_from_outparam__));
             if (v == NULL || numretvals == 1) {
+                Py_XDECREF(tup);
                 Py_DECREF(callargs);
                 return v;
             }