图标不能固定在dark中

[herschel-ma]

bug详情描述
ubuntu 20.04 初步安装后，表现良好，然，更改了dark和plank之后，terminal启动cocomusic出现了以下报错

(cocomusic:72565): Gtk-WARNING **: 18:05:49.136: Theme parsing error: gtk.css:4091:13: negative values are not allowed.

(cocomusic:72565): Gtk-WARNING **: 18:05:49.146: Theme parsing error: gtk.css:7855:13: negative values are not allowed.

(cocomusic:72565): Gtk-WARNING **: 18:05:49.146: Theme parsing error: gtk.css:8039:19: negative values are not allowed.

(cocomusic:72565): Gtk-WARNING **: 18:05:49.148: Theme parsing error: gtk.css:8317:21: negative values are not allowed.

(cocomusic:72565): Gtk-WARNING **: 18:05:49.148: Theme parsing error: gtk.css:8318:24: negative values are not allowed.

发现ubuntu dark中没有coco的图标，但可以正常听歌

如何重现bug呢
美化了下ubuntu,怎么美化的还有点懵比，就是用plank dark代替了原来的

截图
no here

桌面信息:

• 操作系统: [Ubuntu]
• 版本号 [20.04]