Accessing Facebook stuff without a dive selected (as in an empty logbook) just SIGSEGVs. Just be more carefull. After this fix, it is still possible to upload an "empty dive" to FB. Ok, a little pointless, but a nice picture of the Subsurface logo is uploaded to FB. Consider it an easter egg :-) Fixes: #280 Signed-off-by: Jan Mulder <jlmulder@xs4all.nl>