xwm: flush xcb connection only when we processed some event

xwayland source is checked, so it dispatches twice on any event.
If the other turn has no events to dispatch, we flush the connection
redundantly

v2. do not flood logs with 'unhandled event' messages

Signed-off-by: Marek Chalupa <mchqwerty@gmail.com>
Reviewed-by: Derek Foreman <derekf@osg.samsung.com>
Reviewed-by: Bryce Harrington <bryce@osg.samsung.com>
diff --git a/xwayland/window-manager.c b/xwayland/window-manager.c
index f9544d8..db6b437 100644
--- a/xwayland/window-manager.c
+++ b/xwayland/window-manager.c
@@ -1979,7 +1979,8 @@
 		count++;
 	}
 
-	xcb_flush(wm->conn);
+	if (count != 0)
+		xcb_flush(wm->conn);
 
 	return count;
 }