c
< 	memcpy (&this_set[row - 1].signature, ph, sizeof (uint64_t));
---
> 	if (row > 0 && row <= nused) {
> 		uint64_t *signature = &this_set[row - 1].signature;
> 		if (signature != NULL) {
> 			memcpy (signature, ph, sizeof (uint64_t));
> 		}
> 	}
