Your sarcasm is not entertaining. It’s actually quite rude.
Because it makes no sense! Having SketchUp check whether a browser is running and silently omitting information if it’s not would be an extremely arbitrary and illogical connection. Maybe the ding sound when an error occurs should only play if Spotify is running, and if Spotify isn’t running it is assumed the user is in a library or other quiet environment? Sure it could be done but it wouldn’t make any sense.
I care about not impairing SketchUp, which you seem to want.
I have already suggested that busplat makes a request to the SketchUp server to see if there is any additional info to show, and only navigate to the page if there is. I also said the info could perhaps be shown inside BugSplat but gave a few reasons why it isn’t necessarily better.
This assumption is incorrect. When a program (other than the web browser itself) wants to navigate to a web page it passes the URL to the OS and the OS handles what program to call. Then it is up to that program to decide how to handle tabs and saved sessions.
Why are you stuck on this specific implementation? Other solutions have already been suggested.