Fix refcount accounting

Author: markshannon

Include/refcount.h

@@ -307,7 +307,10 @@ static inline Py_ALWAYS_INLINE void Py_INCREF(PyObject *op)
 #endif
     _Py_INCREF_STAT_INC();
 #ifdef Py_REF_DEBUG
-    _Py_INCREF_IncRefTotal();
+    // Don't count the incref if the object is immortal.
+    if (_Py_IsImmortal(op)) {
+        _Py_INCREF_IncRefTotal();
+    }
 #endif
 #endif
 }