Instance map fixes (#3539)

* Fixed #3517, new map from instance doesn't use unused map slots
* Fixed #3528, crashed on reloadscript if there is instance map
* Cleared map flags on reloadscript

src/map/npc.cpp

@@ -4537,6 +4537,7 @@ int npc_reload(void) {
 	//Execute the OnInit event for freshly loaded npcs. [Skotlex]
 	npc_event_runall(script_config.init_event_name);
 
+	map_data_copyall();
 	do_reload_instance();
 
 	// Execute rest of the startup events if connected to char-server. [Lance]