[Confluence] Don't process subsequent onclicks if the first one was cancelled

The subtitles button on the VideOSD has three actions assigned to it.
The first one is to select a subtitle addon. When this select dialog is cancelled, 
don't try to process the other defined actions.

this PR fixes two things:
- change the 'Close' action to 'Dialog.Close(VideoOSD)' as it would potentially close the FullScreenVideo window instead of just the VideoOSD
- don't try to run a subtitles addon if no addon was selected.

Fixes #13576