Created attachment 164877 [details]
Empty dialog when no connection
When you open the additions dialog when you have no internet connection, you see an empty dialog without any feedback for the user.
On terminal I can see this:
warn:cui.dialogs:6638:6718:cui/source/dialogs/AdditionsDialog.cxx:138: Download failed. Error code: 0
warn:cui.dialogs:6638:6718:cui/source/dialogs/AdditionsDialog.cxx:143: curl error: 6
So the error is already handled to some extent. What we need is reflect that message on the UI, either on the task/status area of the dialog at the bottom, or via a message box as warning like "Couldn't get the list of extensions. Please make sure you are connected to the Internet."