Set input shape to 0x0 to passthrough mouse

Define the input shape to be empty so that one cannot click on the grid.
This resolves all issues where the cursor ends up pointing to the grid
itself instead of the window under the grid due to openpixel() not being
called.

keynav.c

@@ -983,6 +983,9 @@ void cmd_start(char *args) {
     /* Tell the window manager not to manage us */
     winattr.override_redirect = 1;
     XChangeWindowAttributes(dpy, zone, CWOverrideRedirect, &winattr);
+    /* Set the input shape to be nothing so that the mouse can still
+     * click/scroll if on the grid */
+    XShapeCombineRectangles(dpy, zone, ShapeInput, 0, 0, NULL, 0, ShapeSet, 0);
 
     XSelectInput(dpy, zone, StructureNotifyMask | ExposureMask
                  | PointerMotionMask | LeaveWindowMask );