Undefined index, when importing existing upper level map which contains link to submap
Steps to reproduce:
1. Create map and submap
2. Export upper level map
3. Import upper level map
4. Open details info in success message
Result: Undefined index: sysmapid [map.import.php:166 ? CApiWrapper->__call() ? CFrontendApiWrapper->callMethod() ? CApiWrapper->callMethod() ? CFrontendApiWrapper->callClientMethod() ? CLocalApiClient->callMethod() ? CConfiguration->import() ? CConfigurationImport->import() ? CConfigurationImport->processMaps() ? CMapImporter->import() ? CMap->update() ? CMapElement->updateSelements() ? CMapElement->checkSelementInput() in include/classes/api/services/CMapElement.php:206]