This is the only case where C-code sets the current file.
Remove this call for a better separation of C-backend and
C++-frontend parts.
There were four callers of clear_dive_file_data(). Two of them
would call set_filename() anyway. For the remaining two add an
explicit call to set_filename().
This commit fixes a bug introduced in commit b3901aa8f90499ee2a34efdddc2463105afc53f1:
The cloud-online menu entry was still enabled after "closing" the
cloud storage.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>