ubuntu 20.04.4系统执行升级命令后全部应用图标都无法显示，系统变成如下图：
很多应用也无法打开了，点击之后无任何反应。
查看系统日志可以看到如下错误信息：
这个原因是由于 gdk-pixbuf 的改动导致的系统 BUG，只需要重新生成一下应用图标缓存即可。
执行如下命令：
参考链接
- Gtk-WARNING **: Could not load a pixbuf from icon theme
- Enable all loaders to be built in by default
- Desktop Installer doesn't start if yaru-theme-icon is not installed on the host #323
- Cannot launch any Ubuntu app and icons missing - Gtk Warning
- After update/upgrade, grim crashes on gtk error
- Various apps crash due to assertion failure in ensure_surface_for_gicon [gtkiconhelper.c:493/494]
- [Solved] Could not load pixbuf from icon theme. gdk error crash
- /usr/bin/gdk-pixbuf-query-loaders is no more available in debian and ubuntu #9