Check permissions for adding player if this admin or has admin rigth/op

[RitaSister]

Please add checking permissions of admin from essentials or other plugins, because player can check for online admins if admin is vanished.

[apehum]

Not sure if I understood you correctly, but I added vanish checks in commands suggestions and player exists checks (b6b3340 and f500278).

Latest build can be downloaded here: https://github.com/plasmoapp/pv-addon-groups/releases/tag/1.1.1.

Note that this fix won't work if the groups addon is installed on the proxy (velocity/bungee).
It requires direct integration with specific vanish plugins and I don't want to deal with it right now.