gh-94673: Fix _PyTypes_InitTypes() and get_type_attr_as_size() (gh-103961)

This change has two small parts:

1. a follow-up to gh-103940 with one case I missed
2. adding a missing return that I noticed while working on related code

Objects/structseq.c

@@ -31,6 +31,7 @@ get_type_attr_as_size(PyTypeObject *tp, PyObject *name)
         PyErr_Format(PyExc_TypeError,
                      "Missed attribute '%U' of type %s",
                      name, tp->tp_name);
+        return -1;
     }
     return PyLong_AsSsize_t(v);
 }