[3.15] gh-154822: Fix racy assertion during finalization (GH-154824) (GH-154828)

(cherry picked from commit cb0f028)

Co-authored-by: Peter Bierma <zintensitydev@gmail.com>

Author: miss-islington

Python/pylifecycle.c

@@ -3820,8 +3820,8 @@ handle_thread_shutdown_exception(PyThreadState *tstate)
     assert(tstate != NULL);
     assert(_PyErr_Occurred(tstate));
     PyInterpreterState *interp = tstate->interp;
-    assert(interp->threads.head != NULL);
     _PyEval_StopTheWorld(interp);
+    assert(interp->threads.head != NULL);
 
     // We don't have to worry about locking this because the
     // world is stopped.