kernel: add missing NULL checks on allocation paths

[palazik]

Two kernel allocation sites dereference their result without checking for failure, which panics the kernel under memory pressure.

1. kernel/manager/throne_tracker.c — my_actor()

struct apk_path_hash *apk_data = kzalloc(sizeof(struct apk_path_hash), GFP_KERNEL);
apk_data->hash = hash;   // NULL deref if kzalloc fails

Every other allocation in this file is checked (e.g. the data_path alloc a few lines above skips the entry on failure). This one wasn't. Fixed by skipping the entry (FILLDIR_ACTOR_CONTINUE) when the allocation fails.

2. kernel/selinux/sepolicy.c — add_filename_trans()

trans = kcalloc(1, sizeof(*trans), GFP_KERNEL);
struct filename_trans_key *new_key = kzalloc(sizeof(*new_key), GFP_KERNEL);
*new_key = key;                        // NULL deref
new_key->name = kstrdup(key.name, ..); // unchecked
trans->next = last;                    // NULL deref

Three unchecked allocations, all dereferenced immediately. Fixed by checking each and bailing out (return false, matching the function's existing error style), freeing the partial allocations on the way out.

Both are OOM-only robustness fixes; no behavior change on the success path.