#14 Error message if no map is included

[Lulu-Ann]

People download LoroDux and install the .jar file without reading the instructions.
This leads to an uncatched error at startup.

LoroDux shall check if map data is included.

If not, it shall show the error Message: "Keine Kartendaten verfügbar. Folgen Sie der in der Zip-Datei enthaltenen Anleitung, um Kartendaten in LoroDux einzufügen."