In function DCsync_item_preproc(DB_RESULT result) can be called uninitialized pointer:
1. Declaring variable item without initializer.

ZBX_DC_ITEM             *item;

2. Condition itemid != lastitemid, taking false branch.

if (itemid != lastitemid && NULL == (item = zbx_hashset_search(&config->items, &itemid)))
continue;

3. Using uninitialized value item.

zbx_vector_ptr_append(&item->preproc_ops, preproc);

(CID 155653, 155648)