Prevent crash when dragging window to the bottom of the column it's already in
Prevent crash when dragging window to the bottom of the column it's already in

wingyplus/wmii,wingyplus/wmii,darkfeline/wmii,darkfeline/wmii,rvedam/wmii,Sirikid/wmii,darkfeline/wmii,darkfeline/wmii,jerluc/wmii,jerluc/wmii,wingyplus/wmii,darkfeline/wmii,sigmavirus24/wmii,rvedam/wmii,Sirikid/wmii,rvedam/wmii,jerluc/wmii,sigmavirus24/wmii,sigmavirus24/wmii,Sirikid/wmii,sigmavirus24/wmii,wingyplus/wmii,Sirikid/wmii,wingyplus/wmii,rvedam/wmii,Sirikid/wmii,sigmavirus24/wmii,rvedam/wmii,jerluc/wmii,jerluc/wmii