Remove useless check in _tree_next

con_descend_focused on an empty workspace should return the workspace.

src/tree.c

@@ -565,10 +565,8 @@ static bool _tree_next(Con *con, char way, orientation_t orientation, bool wrap)
             focus = con_descend_focused(workspace);
         }
 
-        if (focus) {
         con_focus(focus);
         x_set_warp_to(&(focus->rect));
-        }
         return true;
     }