Once the user starts editing a dive site, make sure to pass
coordinates of either the current map center (if a new MapLocation
is being added) or the coordinates of the existing MapLocation.
The "Dive site management" coordinates text field would receive
these new coordinates after the displayed_dive_site struct
is updated and the coordinatesChanged() signal is emitted.
Signed-off-by: Lubomir I. Ivanov <neolit123@gmail.com>