Help to edit random option item drop by mob

[Litro Endemic]

i want to have all equipment drop by mob have random item, as of now it need to be listed by id

and I want it to categorized by equip location, i have trying to make it my self by editing mob_readdb_drop multiple time and it failed and the last try give me Segmentation fault

well here my edited code, well i have no knowledge i'm just trying to make it by my self to learn but it always fail

static bool mob_readdb_drop(char* str[], int columns, int current) {
	unsigned short i;

	for (i = 0; i <= MAX_MOB_DB; i++) {
		int j, size;
		struct mob_db *mob;
		struct s_mob_drop *drop;
		struct item_data *id;
	
		if ((mob = mob_db(i)) == mob_dummy) {
			continue;
		}
	
		drop = mob->dropitem;
		size = ARRAYLENGTH(mob->dropitem);
		
		for (j = 0; j < size; j++) {
			switch(id->equip) {
				case EQP_ARMOR:    drop[j].randomopt_group = RDMOPTG_Armor; break;
				//case EQP_HAND_L:   drop[i].randomopt_group = RDMOPTG_None;
				//case EQP_HAND_R:   drop[i].randomopt_group = RDMOPTG_None;
				//case EQP_GARMENT:  db->dropitem[i].randomopt_group = RDMOPTG_None;
				case EQP_SHOES:    drop[j].randomopt_group = RDMOPTG_Shoes; break;
				//case EQP_ACC_L:    db->dropitem[i].randomopt_group = RDMOPTG_None;
				//case EQP_ACC_R:    db->dropitem[i].randomopt_group = RDMOPTG_Acc;
			}
		}
	}

	return true;
}

please help me...