Test retrieving PyThreadState multiple times from different thread

Author: fangerer

graalpython/com.oracle.graal.python.test/src/tests/cpyext/test_thread.py

@@ -99,6 +99,9 @@ def test_register_new_thread(self):
                 if (!PyObject_CallNoArgs(callable)) {
                     PyErr_WriteUnraisable(callable);
                 }
+                if (PyThreadState_Get() == NULL || PyThreadState_Get() == NULL) {
+                    PyErr_WriteUnraisable(callable);
+                }
                 PyGILState_Release(gstate);
                 return NULL;
             }