Fix some NPC and Corpse falling through the ground issues

zone/bonuses.cpp

@@ -48,6 +48,14 @@ void Mob::CalcBonuses()
 	SetAttackTimer();
 	CalcAC();
 
+	/* Fast walking NPC's are prone to disappear into walls/hills 
+		We set this here because NPC's can cast spells to change walkspeed/runspeed
+	*/
+	float get_walk_speed = static_cast<float>(0.025f * this->GetWalkspeed());
+	if (get_walk_speed >= 0.9 && this->fix_z_timer.GetDuration() != 100) {
+		this->fix_z_timer.SetTimer(100);
+	}
+
 	rooted = FindType(SE_Root);
 }