apisix-dashboard: bug: Network Error prompted up when enable global plugin

Issue description

启用插件和删除上游报错Network Error，有的启动插件报其他的错误

Expected behavior

How to Reproduce

1. Go to ‘插件’
2. Click on ‘启动’
3. Scroll down to ‘任何一个插件’
4. See error

Screenshots

Environment

• apisix version (cmd: apisix version):2.8

• OS (cmd: uname -a):Linux slave1 3.10.0-514.el7.x86_64 #1 SMP Tue Nov 22 16:42:41 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

• OpenResty / Nginx version (cmd: nginx -V or openresty -V):nginx version: openresty/1.19.3.2

• etcd version, if have (cmd: run curl http://127.0.0.1:9090/v1/server_info to get the info from server-info API):3.4.13

• apisix-dashboard version, if have:2.7

• Browser version, if have:

Additional context