Change condition to avoid spurious compiler complaints.

Change condition to avoid spurious compiler complaints.

X509_TRUST_get0() is checking < 0, the code here was checking == -1.  Both are
equivalent in this situation but gcc-12 has conniptions about a subsequent
possible NULL dereference (which isn't possible).

Fixes #17665

Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/17668)

(cherry picked from commit b84c6e86dd8ca88444207080808d1d598856041f)