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
