Can't figure out how to update https://phabricator.kde.org/D894 so I just did this
Some custom map providers will not provide a maps for the entire world , but rather to a small area.
While there is a command line option to start marble to point to a location , it is not a feasible solution when requesting a non technical person to start with command line options (In addition to the need for asking a person to put files a directory).
This patch solve some of the issues raised by devs in the D894