structseq.c: NULL dereference in get_type_attr_as_size

Bug report

Bug description:

Parent: #146102

When PyDict_GetItemWithError returns NULL due to error (not missing key), code falls through to PyLong_AsSsize_t(NULL) at line 37 → segfault. Affects PyStructSequence_New, structseq_new_impl, etc.

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-148119: Refactor get_type_attr_as_size to improve error handling in structseq.c #148120