Fix null pointer deref

Author: mdboom

Include/cpython/tupleobject.h

@@ -36,7 +36,9 @@ PyTuple_SET_ITEM(PyObject *op, Py_ssize_t index, PyObject *value) {
     assert(0 <= index);
     assert(index < Py_SIZE(tuple));
     tuple->ob_item[index] = value;
-    tuple->contains_mortal |= !_Py_IsImmortal(value);
+    if (value != NULL) {
+        tuple->contains_mortal |= !_Py_IsImmortal(value);
+    }
 }
 #define PyTuple_SET_ITEM(op, index, value) \
     PyTuple_SET_ITEM(_PyObject_CAST(op), (index), _PyObject_CAST(value))

Objects/tupleobject.c

@@ -111,7 +111,7 @@ PyTuple_GetItem(PyObject *op, Py_ssize_t i)
         PyErr_SetString(PyExc_IndexError, "tuple index out of range");
         return NULL;
     }
-    return ((PyTupleObject *)op) -> ob_item[i];
+    return ((PyTupleObject *)op)->ob_item[i];
 }
 
 int