Fix the problem regarding installing addons

[secretwolfie]

When installing workshop addons, it asks the user to stop the server, if they click No, the program proceeds to install the addon onto the server. This has caused corruption and chaos on my system.

I suggest one of the following:

Instead of asking the user to stop the server after they've picked the item for install, stop the user from even installing addons to begin with. If the user wants to install addons, instruct the user to stop the server first.

OR: Have the current request box, but instead of it proceeding after clicking no, do not let it proceed, cancel the request.

Hopefully this will clear this bug.