Clear awaiter pointers in SEND_GEN

Summary:
Inline completed coroutines retain stale awaiter pointers. Fixed it by
clearing them

Reviewed By: alexmalyshev

Differential Revision: D112393428

fbshipit-source-id: 0b86997da373eb245a1137a59762bee2ca78f73c

Author: czardoz

cinderx/Interpreter/3.12/Includes/ceval.c

@@ -1577,6 +1577,8 @@ clear_gen_frame(PyThreadState *tstate, _PyInterpreterFrame * frame)
     _PyFrame_ClearExceptCode(frame);
     tstate->c_recursion_remaining++;
     frame->previous = NULL;
+    /* Inlined SEND bypasses gen_send_ex2(), so clear the awaiter here. */
+    Py_CLEAR(gen->gi_ci_awaiter);
 }
 
 static void