Corrected damage immunity states (fixes #1754)

* Added unit data damage immunity to the GvG targeting function.
* Added unit data and mob mode damage immunity to the reflecting damage calculation function.
Thanks to @admkakaroto!

src/map/battle.c

@@ -1598,8 +1598,11 @@ int64 battle_calc_bg_damage(struct block_list *src, struct block_list *bl, int64
 bool battle_can_hit_gvg_target(struct block_list *src,struct block_list *bl,uint16 skill_id,int flag)
 {
 	struct mob_data* md = BL_CAST(BL_MOB, bl);
+	struct unit_data *ud = unit_bl2ud(bl);
 	int class_ = status_get_class(bl);
 
+	if (ud && ud->immune_attack)
+		return false;
 	if(md && md->guardian_data) {
 		if ((status_bl_has_mode(bl,MD_SKILL_IMMUNE) || (class_ == MOBID_EMPERIUM && !(skill_get_inf3(skill_id)&INF3_HIT_EMP))) && flag&BF_SKILL) //Skill immunity.
 			return false;
@@ -5169,13 +5172,15 @@ void battle_do_reflect(int attack_type, struct Damage *wd, struct block_list* sr
 		struct map_session_data *tsd = BL_CAST(BL_PC, target);
 		struct status_change *tsc = status_get_sc(target);
 		struct status_data *sstatus = status_get_status_data(src);
+		struct unit_data *ud = unit_bl2ud(target);
 		int tick = gettick(), rdelay = 0;
 
 		if (!tsc)
 			return;
 
 		// Calculate skill reflect damage separately
-		rdamage = battle_calc_return_damage(target, src, &damage, wd->flag, skill_id,true);
+		if ((ud && !ud->immune_attack) || !status_bl_has_mode(target, MD_SKILL_IMMUNE))
+			rdamage = battle_calc_return_damage(target, src, &damage, wd->flag, skill_id,true);
 		if( rdamage > 0 ) {
 			struct block_list *d_bl = battle_check_devotion(src);