only FocusChangeMask|PropertyChangeMask if needed

We don't need to listen to the corresponding events when we don't need
to follow the mouse/keyboard focus.

x.c

@@ -805,9 +805,11 @@ void x_win_setup(void)
                    (unsigned long)((100 - settings.transparency) *
                                    (0xffffffff / 100)));
 
+        if (settings.f_mode != FOLLOW_NONE) {
                 long root_event_mask = FocusChangeMask | PropertyChangeMask;
                 XSelectInput(xctx.dpy, root, root_event_mask);
         }
+}
 
         /*
          * Show the window and grab shortcuts.