Question about `libcrun_error_t *err` input argument requirement

Many crun() functions takes ` libcrun_error_t *err` as input argument.

Is there a requirement to set `err` to `NULL` beforehand?

In other words, is it required to do
```
libcrun_error_t err = NULL;
some_crun_function (&err);
```
or is it also fine to do this?

```
libcrun_error_t err;
some_crun_function (&err);
```

For example, it seems this code has the NULL requirement:

https://github.com/containers/crun/blob/0aef8e17e0925806ae4577d9a82a7b326c185910/src/libcrun/linux.c#L1323

because this code

https://github.com/containers/crun/blob/0aef8e17e0925806ae4577d9a82a7b326c185910/src/libcrun/error.c#L104

would otherwise dereference an uninitialized pointer.

If there is such a requirement, then it is not documented in `error_handling.md`

https://github.com/containers/crun/blob/0aef8e17e0925806ae4577d9a82a7b326c185910/design-docs/error_handling.md?plain=1#L1-L20

See also

* https://github.com/containers/crun/issues/2022

that discussed dereferencing an uninitialized pointer because of

```
libcrun_error_t err;
```

in _python/crun_python.c_

Read design-docs/error_handling.md alongside the cited code in src/libcrun/linux.c and src/libcrun/error.c, then compare the call pattern with _python/crun_python.c. Confirm the required initialization behavior and document the requirement, including a safe example, in error_handling.md.

Written by the indexing model from the issue text.