SEXP item in system_info may be uninitialized

```
20. openscap-1.2.13/src/OVAL/probes/independent/system_info.c:696: uninit_use_in_call: Using uninitialized value "item" when calling "SEXP_free".
19. openscap-1.2.13/src/OVAL/probes/independent/system_info.c:695: uninit_use_in_call: Using uninitialized value "item" when calling "get_ifs".
```

This is a minor issue but may cause a segfault when handling errors.