[PATCH] libctf: Return CTF_ERR in ctf_type_resolve_unsliced PR 30836

[Nick Alcock]

On 17 Oct 2023, Torbjörn SVENSSON uttered the following:

> There were one more place where the incorrect return value was used.
>
> @Nick: Ok for trunk? :)

By all means: push away. Dead obvious too, right above a correct one,
and I still overlooked it.

(I just checked for further instances of this in ctf-types.c and could
see none.)