Fix segfault in has_torch_function (#88559)

Fixes #83908

`PySequence_Fast` may return `NULL` to indicate an error was raised, in which
case `sequence_has_torch_function` will dereference a null pointer.

Pull Request resolved: https://github.com/pytorch/pytorch/pull/88559
Approved by: https://github.com/ezyang, https://github.com/Skylion007, https://github.com/hameerabbasi

torch/csrc/utils/disable_torch_function.cpp

@@ -263,6 +263,9 @@ PyObject* THPModule_has_torch_function(PyObject*, PyObject* arg) {
   } else {
     auto args = py::reinterpret_steal<py::object>(
         PySequence_Fast(arg, "expected a sequence"));
+    if (!args) {
+      return nullptr;
+    }
     result = sequence_has_torch_function(args.ptr());
   }