When changing the selection the MapLocationModel was reset.
This lead to crashes on Qt-5.9 which are due to QML accessing
data that was freed during model reset. This putative Qt bug
doesn't happen on newer Qt versions. At least Qt-5.12 is known
to work.
Instead of fighting the bug, let's simply not reset the model
but send a dataChanged() for every element of the MapLocationModel.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>