[World API] Input Validation (#4904)

* [World API] Input Validation

* Update eqemu_api_world_data_service.cpp

* Add db ping to player events processor, move back into main thread

world/eqemu_api_world_data_service.cpp

@@ -24,6 +24,10 @@ void callGetZoneList(Json::Value &response)
 	for (auto &zone: zoneserver_list.getZoneServerList()) {
 		Json::Value row;
 
+		if (!zone) {
+			continue;
+		}
+
 		if (!zone->IsConnected()) {
 			continue;
 		}