only try and toggle fullscreen if a valid window is focused
only try and toggle fullscreen if a valid window is focused

cHoco/kwm,a-morales/kwm,akdor1154/kwm,koekeishiya/kwm,a-morales/kwm,cHoco/kwm,akdor1154/kwm,koekeishiya/kwm,a-morales/kwm,cHoco/kwm,akdor1154/kwm,koekeishiya/kwm