Don't complain on '-z' if there's no lastwallpaper
Don't complain on '-z' if there's no lastwallpaper

This hides the odd cornercase of users with no lastwallpaper file and no
background set in their style or overlay.

Adapted from the patch at
http://sourceforge.net/tracker/?func=detail&aid=2389567&group_id=35398&atid=413962

olivergondza/fluxbox,lukoko/fluxbox,olivergondza/fluxbox,olivergondza/fluxbox,lukoko/fluxbox,luebking/fluxbox,Arkq/fluxbox,naimdjon/fluxbox,luebking/fluxbox,lukoko/fluxbox,Arkq/fluxbox,naimdjon/fluxbox,naimdjon/fluxbox,Arkq/fluxbox,luebking/fluxbox,Arkq/fluxbox,naimdjon/fluxbox,luebking/fluxbox,naimdjon/fluxbox,olivergondza/fluxbox,luebking/fluxbox,lukoko/fluxbox,Arkq/fluxbox,olivergondza/fluxbox,lukoko/fluxbox