The DiveHandler shows a context menu where a cylinder can be
chosen. This indirectly accesses the global displayed_dive
variable.
Remove this in a step to make the profile reentrant.
The code was quite ominous: instead of simply generating the
list of cylinders, a global model was reset and then accessed
with Qt's cumbersome model/view API. All this trampling over
global state can be removed by simply making the function
that generates the list globally accessible.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>