Don't try to create a mask out of null rects

This may happen if the window is destroyed at just the right moment.

diff --git a/source/main.c b/source/main.c
index f7688b9eb920414f4695d9014b000640bf940289..cd2f1acb5a085bec2e8d33d30fbd49844382e7cd 100644 (file)
--- a/source/main.c
+++ b/source/main.c
@@ -422,6 +422,8 @@ void update_window_mask(Compositor *compositor, CompositedWindow *window)
                return;
 
        rects = XShapeGetRectangles(compositor->display, window->window, ShapeBounding, &rect_count, &rect_order);
+       if(!rects)
+               return;
 
        width = window->width+2*window->border;
        height = window->height+2*window->border;