If the entries in the DiveLocationModel don't have their entries
set as editable, the auto-completion popup turns of composition
if such an item is highlighted (see Qt code in
/src/widgets/itemviews/qabstractitemview.cpp), thus disabling
composition of multi-key characters.
Therefore, set this flag. Seems weird, but what should we do!?
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>