Bugfix: NULL dereference when stickying _NET_WM_DESKTOP_ALL windows (#2488)
Bugfix: NULL dereference when stickying _NET_WM_DESKTOP_ALL windows (#2488)

In some cases, ws will be NULL here.

Originally tested with "lemonbar"
shdown/i3,stapelberg/i3,acrisci/i3,strake/i3,i3/i3,Airblader/i3-original,stapelberg/i3,Airblader/i3,Airblader/i3-original,acrisci/i3,Airblader/i3-original,i3/i3,strake/i3,avrelaun/i3,cornerman/i3,acrisci/i3,Airblader/i3-original,acrisci/i3,i3/i3,cornerman/i3,cornerman/i3,shdown/i3,strake/i3,avrelaun/i3,strake/i3,Airblader/i3,stapelberg/i3,strake/i3,cornerman/i3,Airblader/i3-original,avrelaun/i3,avrelaun/i3,stapelberg/i3,Airblader/i3,shdown/i3,Airblader/i3,acrisci/i3,i3/i3,shdown/i3