* Fix NULL pointer access when H5A_operator2_t is NULL
Passing NULL for the callback function pointer to H5Aiterate2 and
H5Aiterate_by_name was not detected, leading to a subsequent access
of an uninitialized pointer. Add a check for this "no operator
specified" case in both functions so they fail gracefully instead.
Fixes GHSA-r7g4-hv2f-5c66 - CVE-2025-9274
* Fix format
* Fix Java test to handle NULL callback to H5Aiterate2